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Heckler C, Vale MG, Canales HDS, Stradiotto GC, Giordano ALPL, Schreiber AZ, Sant'Ana AS. Spore-forming bacteria in gelatin: Characterization, identification by 16S rRNA and MALDI-TOF mass spectrometry (MS), and presence of heat resistance and virulence genes. Int J Food Microbiol 2024; 422:110813. [PMID: 38970997 DOI: 10.1016/j.ijfoodmicro.2024.110813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 06/20/2024] [Accepted: 06/27/2024] [Indexed: 07/08/2024]
Abstract
Gelatin, a versatile protein derived from collagen, is widely used in the food, pharmaceutical and medical sectors. However, bacterial contamination by spore-forming bacteria during gelatin processing represents a significant concern for product safety and quality. In this study, an investigation was carried out to explore the heat and chemical resistance, as well as the identification and characterization of spore-forming bacteria isolated from gelatin processing. The methodologies involved chemical resistance tests with drastic pH in microplates and thermal resistance tests in capillary tubes of various isolates obtained at different processing stages. In addition, phenotypic and genotypic analyses were carried out to characterize the most resistant isolates of spore-forming bacteria. The findings of this study revealed the presence of several species, including Bacillus cereus, Bacillus licheniformis, Bacillus sonorensis, Bacillus subtilis, Geobacillus stearothermophilus, and Clostridium sporogenes, with some isolates exhibiting remarkable chemical and heat resistances. In addition, a significant proportion of the most resistant isolates showed gelatinase activity (n = 19/21; 90.5 %) and the presence of heat resistance (n = 5/21; 23.8 %), and virulence genes (n = 11/21; 52.4 %). The results of this study suggest that interventions should be done in quality control practices and that process parameter adjustments and effective contamination reduction strategies should be implemented through gelatin processing.
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Affiliation(s)
- Caroline Heckler
- Department of Food Science and Nutrition, Faculty of Food Engineering, University of Campinas, Campinas, São Paulo, Brazil
| | - Matheus G Vale
- Department of Integrated Systems, Faculty of Mechanical Engineering, University of Campinas, Campinas, São Paulo, Brazil
| | - Héctor D S Canales
- Department of Food Science and Nutrition, Faculty of Food Engineering, University of Campinas, Campinas, São Paulo, Brazil
| | - Graziele C Stradiotto
- Department of Food Science and Nutrition, Faculty of Food Engineering, University of Campinas, Campinas, São Paulo, Brazil
| | - Ana Luisa P L Giordano
- Department of Clinical Pathology, Faculty of Medical Sciences, University of Campinas, Campinas, São Paulo, Brazil
| | - Angelica Z Schreiber
- Department of Clinical Pathology, Faculty of Medical Sciences, University of Campinas, Campinas, São Paulo, Brazil
| | - Anderson S Sant'Ana
- Department of Food Science and Nutrition, Faculty of Food Engineering, University of Campinas, Campinas, São Paulo, Brazil.
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2
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Finton M, Skeie SB, Aspholm ME, Franklin-Alming FV, Mekonnen YB, Kristiansen H, Porcellato D. Two-year investigation of spore-formers through the production chain at two cheese plants in Norway. Food Res Int 2024; 190:114610. [PMID: 38945575 DOI: 10.1016/j.foodres.2024.114610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 06/04/2024] [Accepted: 06/04/2024] [Indexed: 07/02/2024]
Abstract
Spore-forming bacteria are the most complex group of microbes to eliminate from the dairy production line due to their ability to withstand heat treatment usually used in dairy processing. These ubiquitous microorganisms have ample opportunity for multiple points of entry into the milk chain, creating issues for food quality and safety. Certain spore-formers, namely bacilli and clostridia, are more problematic to the dairy industry due to their possible pathogenicity, growth, and production of metabolites and spoilage enzymes. This research investigated the spore-forming population from raw milk reception at two Norwegian dairy plants through the cheesemaking stages until ripening. Samples were collected over two years and examined by amplicon sequencing in a culture independent manner and after an anaerobic spore-former enrichment step. In addition, a total of 608 isolates from the enriched samples were identified at the genus or species level using MALDI-TOF analysis. Most spore-forming isolates belong to the genera Bacillus or Clostridium, with the latter dominating the enriched MPN tubes of raw milk and bactofugate. Results showed a great variation among the clostridia and bacilli detected in the enriched MPN tubes. However, B. licheniformis and C. tyrobutyricum were identified in all sample types from both plants throughout the 2-year study. In conclusion, our results shed light on the fate of different spore-formers at different processing stages in the cheese production chain, which could facilitate targeted actions to reduce quality problems.
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Affiliation(s)
- Misti Finton
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | - Siv Borghild Skeie
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | - Marina Elisabeth Aspholm
- Department of Paraclinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | | | - Yohannes Beyene Mekonnen
- Department of Paraclinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | - Hanne Kristiansen
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | - Davide Porcellato
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway.
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3
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Delaunay L, Postollec F, Leguérinel I, Mathot AG. Detection of risk areas in dairy powder processes: The development of thermophilic spore forming bacteria taking into account their growth limits. Int J Food Microbiol 2024; 418:110716. [PMID: 38669747 DOI: 10.1016/j.ijfoodmicro.2024.110716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 04/16/2024] [Accepted: 04/21/2024] [Indexed: 04/28/2024]
Abstract
Anoxybacillus flavithermus, Geobacillus stearothermophilus and Bacillus licheniformis are the main contaminants found in dairy powders. These spore-forming thermophilic bacteria, rarely detected in raw milk, persist, and grow during the milk powder manufacturing process. Moreover, in the form of spores, these species resist and concentrate in the powders during the processes. The aim of this study was to determine the stages of the dairy powder manufacturing processes that are favorable to the growth of such contaminants. A total of 5 strains were selected for each species as a natural contaminant of dairy pipelines in order to determine the minimum and maximum growth enabling values for temperature, pH, and aw and their optimum growth rates in milk. These growth limits were combined with the environmental conditions of temperature, pH and aw encountered at each step of the manufacture of whole milk, skim milk and milk protein concentrate powders to estimate growth capacities using cardinal models and the Gamma concept. These simulations were used to theoretically calculate the population sizes reached for the different strains studied at each stage in between two successive cleaning in place procedures. This approach highlights the stages at which risk occurs for the development of spore-forming thermophilic bacterial species. During the first stages of production, i.e. pre-treatment, pasteurization, standardization and pre-heating before concentration, physico-chemical conditions encountered are suitable for the development and growth of A. flavithermus, G. stearothermophilus and B. licheniformis. During the pre-heating stage and during the first effects in the evaporators, the temperature conditions appear to be the most favorable for the growth of G. stearothermophilus. The temperatures in the evaporator during the last evaporator effects are favorable for the growth of B. licheniformis. In the evaporation stage, low water activity severely limits the development of A. flavithermus.
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Affiliation(s)
- Louis Delaunay
- Univ Brest, INRAE, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, 29000 Quimper, France
| | - Florence Postollec
- ADRIA Food Technology Institute, UMT ACTIA 19.03 ALTER'iX, Z.A. de Creac'h Gwen, 29196, Quimper, Cedex, France
| | - Ivan Leguérinel
- Univ Brest, INRAE, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, 29000 Quimper, France.
| | - Anne-Gabrielle Mathot
- Univ Brest, INRAE, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, 29000 Quimper, France
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4
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Choi D, Kong M. LysGR1, a novel thermostable endolysin from Geobacillus stearothermophilus bacteriophage GR1. Front Microbiol 2023; 14:1178748. [PMID: 37275144 PMCID: PMC10237291 DOI: 10.3389/fmicb.2023.1178748] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 05/02/2023] [Indexed: 06/07/2023] Open
Abstract
Geobacillus stearothermophilus is a highly thermophilic, spore-forming Gram-positive bacterium that causes flat sour spoilage in low-acid canned foods. To address this problem, we isolated G. stearothermophilus-infecting phage GR1 from the soil and characterized its endolysin LysGR1. Phage GR1 belongs to the Siphoviridae family and possesses a genome of 79,387 DNA bps with 108 putative open reading frames. GR1 demonstrated a very low degree of homology to previously reported phages, indicating that it is novel. The endolysin of GR1 (LysGR1) contains an N-terminal amidase domain as an enzymatically active domain (EAD) and two C-terminal LysM domains as a cell wall binding domain (CBD). Although GR1 is specific to certain strains of G. stearothermophilus, LysGR1 showed a much broader lytic range, killing all the tested strains of G. stearothermophilus and several foodborne pathogens, such as Clostridium perfringens, Listeria monocytogenes, and Escherichia coli O157:H7. LysGR1_EAD, alone, also exhibits lytic activity against a wide range of bacteria, including Bacillus cereus, which is not terminated by a full-length endolysin. Both LysGR1 and its EAD effectively remove the G. stearothermophilus biofilms and are highly thermostable, retaining about 70% of their lytic activity after a 15-min incubation at 70°C. Considering the high thermal stability, broad lytic activity, and biofilm reduction efficacy of LysGR1 and its EAD, we hypothesize that these enzymes could act as promising biocontrol agents against G. stearothermophilus and as foodborne pathogens.
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5
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Adamski P, Byczkowska-Rostkowska Z, Gajewska J, Zakrzewski AJ, Kłębukowska L. Prevalence and Antibiotic Resistance of Bacillus sp. Isolated from Raw Milk. Microorganisms 2023; 11:microorganisms11041065. [PMID: 37110488 PMCID: PMC10143217 DOI: 10.3390/microorganisms11041065] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 03/24/2023] [Accepted: 04/17/2023] [Indexed: 04/29/2023] Open
Abstract
Milk, due to its diversity in terms of its nutritional content, is an important element of the human diet, as well as a good medium for the development of bacteria. The genus Bacillus contains ubiquitous aerobic, rod-shaped, endospore-producing gram-positive bacteria. Representatives of the Bacillus cereus group and the Bacillus subtilis group contribute to shortening the shelf life of milk and dairy products by degrading milk components and its additives. They also produce a number of heat-stable toxins and can cause a number of ailments, mainly in the digestive system. The aim of this research was to identify Bacillus sp. strains isolated from raw milk and to determine their antibiotic resistance. Strains isolated from raw milk samples (n = 45) were identified by MALDI-TOF MS. Ninety strains of Bacillus sp. were identified, for which the antibiotic resistance phenotype was determined. A total of 90 strains of Bacillus were classified in five groups (the Bacillus cereus group (n = 35), B. licheniformis (n = 7), the B. subtilis group (n = 29), B. pumilus (n = 16), and Bacillus sp. (n = 3). All isolates were susceptible to chloramphenicol and meropenem. The antibiotic resistance profiles of the tested groups of Bacillus spp. differed from each other, which is of particular concern in relation to multidrug-resistant representatives of the B. cereus group resistant to cefotaxime (94.29%), ampicillin (88.57%), rifampicin (80%), and norfloxacin (65.71%). Our study provides data on the prevalence and antibiotic sensitivity of Bacillus sp. In raw milk, suggesting a potential risk to health and the dairy industry.
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Affiliation(s)
- Patryk Adamski
- Department of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury, Plac Cieszyński 1, 10-726 Olsztyn, Poland
| | - Zuzanna Byczkowska-Rostkowska
- Department of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury, Plac Cieszyński 1, 10-726 Olsztyn, Poland
| | - Joanna Gajewska
- Department of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury, Plac Cieszyński 1, 10-726 Olsztyn, Poland
| | - Arkadiusz Józef Zakrzewski
- Department of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury, Plac Cieszyński 1, 10-726 Olsztyn, Poland
| | - Lucyna Kłębukowska
- Department of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury, Plac Cieszyński 1, 10-726 Olsztyn, Poland
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6
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Pramularsih I, Kyere EO, Md Zain SN, Flint S. Testing for total bacteria in dairy powder - Comparison of test incubation temperatures (a case study). Int Dairy J 2022. [DOI: 10.1016/j.idairyj.2022.105452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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7
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Karaca B, Karakaya AB, Ozcan B, Coleri Cihan A. Rapid detection of
Geobacillus
and
Anoxybacillus
species by
quantitative qPCR (qPCR)
in commercial dairy products. J Food Saf 2022. [DOI: 10.1111/jfs.12964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Basar Karaca
- Department of Biology, Faculty of Sciences Ankara University Ankara Turkey
| | | | - Birgul Ozcan
- Department of Biology, Faculty of Art and Sciences Mustafa Kemal University Antakya Turkey
| | - Arzu Coleri Cihan
- Department of Biology, Faculty of Sciences Ankara University Ankara Turkey
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8
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Dynamic tracing of bacterial community distribution and biofilm control of dominant species in milk powder processing. Lebensm Wiss Technol 2022. [DOI: 10.1016/j.lwt.2021.112855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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9
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Wang N, Jin Y, He G, Yuan L. Development of multi-species biofilm formed by thermophilic bacteria on stainless steel immerged in skimmed milk. Food Res Int 2021; 150:110754. [PMID: 34865772 DOI: 10.1016/j.foodres.2021.110754] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/22/2021] [Accepted: 10/10/2021] [Indexed: 11/26/2022]
Abstract
Thermophilic bacteria, such as Bacillus licheniformis, Geobacillus stearothermophilus, Bacillus Subtilis and Anoxybacillus flavithermus, are detected frequently in milk powder products. Biofilms of those strains act as a major contamination to milk powder manufactures and pose potential risks in food safety. In this study, we explored the developing process of multi-species biofilm formed by the four thermophilic bacteria on stainless steel immerged in skimmed milk. The results showed that the thermophilic strains possessed strong capacities to decompose proteins and lactose in skimmed milk, and the spoilage effects were superimposed from multiple strains. B. licheniformis was the most predominant species in the mixed-species biofilm after 12-h incubation. From 24 h to 48 h, G. stearothermophilus occupied the highest proportion. Within the multi-species biofilm, competitive relation existed between B. licheniformis and G. stearothermophilus, while synergistic impacts were observed between B. licheniformis and A. flavithermus. The interspecies mutual influences on biofilm development provided important evidences for understanding colonization of the predominant thermophilic bacteria during milk powder processing.
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Affiliation(s)
- Ni Wang
- School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
| | - Yujie Jin
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Guoqing He
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
| | - Lei Yuan
- College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China.
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10
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Misiou O, Kasiouras G, Koutsoumanis K. Development and validation of an extended predictive model for the effect of pH and water activity on the growth kinetics of Geobacillus stearothermophilus in plant-based milk alternatives. Food Res Int 2021; 145:110407. [PMID: 34112410 DOI: 10.1016/j.foodres.2021.110407] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 04/06/2021] [Accepted: 05/06/2021] [Indexed: 11/17/2022]
Abstract
The cardinal model for the effect of temperature on Geobacillus stearothermophilus ATCC 7953 growth developed by Kakagianni, Gougouli, & Koutsoumanis, 2016 was expanded for the effect of pH and water activity (aw). The effect of pH (range: 5.7-8.5) and aw (range: 0.985-0.999) on G. stearothermophilus growth rate was studied in tryptone soy broth (TSB) using the Bioscreen C method and further modelled using a Cardinal Model (CM). The estimated values for the cardinal parameters [Formula: see text] , and [Formula: see text] were 5.65 ± 0.14, 6.74 ± 0.03, 8.71 ± 0.03, 0.984 ± 0.007 and 0.998 ± 0.001, respectively. The growth behaviour of G. stearothermophilus was investigated in 7 commercial non-refrigerated plant-based milk alternatives under static conditions (62 °C) and the estimated maximum specific growth rates were used to determine the optimum growth rate for each product. The developed model was validated against observed growth of G. stearothermophilus in the 7 products during storage at non-isothermal conditions (testing 4 different temperature profiles). The validation results showed a good performance of the model with overall Bias factor (Bf) = 1.06 and Accuracy factor (Af) = 1.12. The developed model can be used as an effective tool by the food industry in predicting spoilage of plant-based milk alternatives during distribution and storage at retail and domestic levels.
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Affiliation(s)
- Ourania Misiou
- Laboratory of Food Microbiology and Hygiene, Department of Food Science & Technology, Faculty of Agriculture, Aristotle University, 54124 Thessaloniki, Greece
| | - Georgios Kasiouras
- Laboratory of Food Microbiology and Hygiene, Department of Food Science & Technology, Faculty of Agriculture, Aristotle University, 54124 Thessaloniki, Greece
| | - Konstantinos Koutsoumanis
- Laboratory of Food Microbiology and Hygiene, Department of Food Science & Technology, Faculty of Agriculture, Aristotle University, 54124 Thessaloniki, Greece.
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11
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Delaunay L, Cozien E, Gehannin P, Mouhali N, Mace S, Postollec F, Leguerinel I, Mathot AG. Occurrence and diversity of thermophilic sporeformers in French dairy powders. Int Dairy J 2021. [DOI: 10.1016/j.idairyj.2020.104889] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Murphy SI, Kent D, Skeens J, Wiedmann M, Martin NH. A standard set of testing methods reliably enumerates spores across commercial milk powders. J Dairy Sci 2020; 104:2615-2631. [PMID: 33358815 DOI: 10.3168/jds.2020-19313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 10/01/2020] [Indexed: 11/19/2022]
Abstract
Contamination of dairy powders with sporeforming bacteria is a concern for dairy processors who wish to penetrate markets with stringent spore count specifications (e.g., infant powders). Despite instituted specifications, no standard methodology is used for spore testing across the dairy industry. Instead, a variety of spore enumeration methods are in use, varying primarily by heat-shock treatments, plating method, recovery medium, and incubation temperature. Importantly, testing the same product using different methodologies leads to differences in spore count outcomes, which is a major issue for those required to meet specifications. As such, we set out to identify method(s) to recommend for standardized milk powder spore testing. To this end, 10 commercial milk powders were evaluated using methods varying by (1) heat treatment (e.g., 80°C/12 min), (2) plating method (e.g., spread plating), (3) medium type (e.g., plate count milk agar), and (4) incubation time and temperature combinations (e.g., 32°C for 48 h). The resulting data set included a total of 48 methods. With this data set, we used a stepwise process to identify optimal method(s) that would explain a high proportion of variance in spore count outcomes and would be practical to implement across the dairy industry. Ultimately, spore pasteurized mesophilic spore count (80°C/12 min, incubated at 32°C for 48 h), highly heat resistant thermophilic spore count (100°C/30 min, incubated at 55°C for 48 h), and specially thermoresistant spore enumeration (106°C/30 min, incubated at 55°C for 48 h) spread plating on plate count milk agar were identified as the optimal method set for reliable enumeration of spores in milk powders. Subsequently, we assessed different powder sampling strategies as a way to reduce variation in powder spore testing outcomes using our recommended method set. Results indicated that 33-g composite sampling may reduce variation in spore testing outcomes for highly heat resistant thermophilic spore count over 11-g and 33-g discrete sampling, whereas there was no significant difference across sampling strategies for specially thermoresistant spore enumeration or spore pasteurized mesophilic spore count. Finally, an interlaboratory study using our recommended method set and a modified method set (using tryptic soy agar with 1% starch) among both university and industry laboratories showed increased variation in spore count outcomes within milk powders, which not only was due to natural variation in powders but also was hypothesized to be due to technical errors, highlighting the need for specialized training for technicians who perform spore testing on milk powders. Overall, this study addresses challenges to milk powder spore testing and recommends a method set for standardized spore testing for implementation across the dairy industry.
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Affiliation(s)
- S I Murphy
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853
| | - D Kent
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853
| | - J Skeens
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853
| | - M Wiedmann
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853
| | - N H Martin
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853.
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13
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Skeens JW, Wiedmann M, Martin NH. Spore-Forming Bacteria Associated with Dairy Powders Can Be Found in Bacteriological Grade Agar-Agar Supply. J Food Prot 2020; 83:2074-2079. [PMID: 32663274 DOI: 10.4315/jfp-20-195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 07/12/2020] [Indexed: 11/11/2022]
Abstract
ABSTRACT Thermophilic spore-forming bacteria are found ubiquitously in natural environments and, therefore, are present in a number of agricultural food products. Spores produced by these bacteria can survive harsh environmental conditions encountered during food processing and have been implicated in food spoilage. During research efforts to develop a standardized method for enumerating spores in dairy powders, the dairy powder-associated thermophilic sporeformer Anoxybacillus flavithermus was discovered growing in uninoculated control plates of tryptic soy agar (TSA) supplemented with 1% (w/v) starch, after incubation at thermophilic (55°C) growth temperatures. This article reports the investigation into the source of this thermophilic sporeformer in TSA medium components and characterization of the bacterial isolates collected. Aqueous solutions of tryptic soy broth powder from four suppliers and four agar-agar powders (two manufacturing lots from one supplier [agar A_1 and agar A_2] and two from separate suppliers [agar B and agar C]) were subjected to two different autoclave cycle times (121°C for 15 min or 121°C for 30 min) and then prepared as TSA. After incubation at 55°C for 48 h, bacterial growth was observed only in media prepared from both lots of agar A agar-agar powder, and only when they were subjected to a 15-min autoclave cycle, implicating these powders as a source of the sporeformer contamination. Genetic characterization of 49 isolates obtained indicated the presence of five unique rpoB allelic types of the thermophilic sporeformer Geobacillus spp. in agar-agar powder from agar A. These results not only highlight the importance of microbiological controls but also alert researchers to the potential for survival of thermophilic sporeformers such as Anoxybacillus and Geobacillus in microbiological media used for detection and enumeration of these same thermophilic sporeformers in products such as dairy powders. HIGHLIGHTS
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Affiliation(s)
- Jordan W Skeens
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, New York 14853, USA.,(ORCID: https://orcid.org/0000-0002-7672-0982 [J.W.S.])
| | - Martin Wiedmann
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, New York 14853, USA
| | - Nicole H Martin
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, New York 14853, USA
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14
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Dettling A, Wedel C, Huptas C, Hinrichs J, Scherer S, Wenning M. High counts of thermophilic spore formers in dairy powders originate from persisting strains in processing lines. Int J Food Microbiol 2020; 335:108888. [DOI: 10.1016/j.ijfoodmicro.2020.108888] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 07/03/2020] [Accepted: 09/05/2020] [Indexed: 12/15/2022]
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15
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Wang N, Gao J, Yuan L, Jin Y, He G. Metabolomics profiling during biofilm development of Bacillus licheniformis isolated from milk powder. Int J Food Microbiol 2020; 337:108939. [PMID: 33160113 DOI: 10.1016/j.ijfoodmicro.2020.108939] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 10/23/2022]
Abstract
Bacillus licheniformis is a major source of microbial contamination to dairy industry, and biofilm formation by this spoilage bacterium aggravates the safety issues. Especially for milk powder manufactures, the evaporation process at temperatures between 50 °C and 70 °C before spray drying, is a critical control point against thermophilic bacteria multiplication. In our study, metabolomics analysis was performed to investigate dynamic changes of the metabolites and their roles during process of biofilm development of B. licheniformis at 55 °C for 24 h. Amino acid metabolism was quite active, with cooperation from lipid metabolism, carbohydrate metabolism and nucleotide metabolism. Amino acid biosynthesis provided significant contributions especially during early biofilm development from 8 to 12 h. Metabolites involved in specific pathways of arginine biosynthetic, galactose metabolism and sphingolipid metabolism played a crucial role in building biofilm. This work provided new insights into dynamic metabolic alternations and a comprehensive network during B. licheniformis biofilm development, which will extend the knowledge on the metabolic process of biofilm formation by B. licheniformis. The results are helpful in creating better environmental hygiene in dairy processing and new strategies for ensuring quality of dairy products.
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Affiliation(s)
- Ni Wang
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Jie Gao
- College of Food Science and Technology, Hebei Agriculture University, Baoding 071000, China
| | - Lei Yuan
- College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China
| | - Yujie Jin
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Guoqing He
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
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16
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Benahmed M, Leguerinel I, Moussa‐Boudjemaa B. Biodiversity, spoilage capacity and heat resistance of mesophilic aerobic spores isolated from milk powders marketed in Algeria. INT J DAIRY TECHNOL 2020. [DOI: 10.1111/1471-0307.12715] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Meryem Benahmed
- Laboratoire de Microbiologie Appliquée à l'Agroalimentaire et à l'Environnement (LAMAABE) Faculté des SNV/STU Université de Tlemcen BP119 13000 Tlemcen Algeria
- Centre universitaire de Ain‐Témouchent route de Sidi Bel‐Abbès N°101 46000 Ain‐Témouchent Algeria
| | - Ivan Leguerinel
- Laboratoire Universitaire de Biodiversité et Écologie Microbienne EA 3882 UMT ALTER'IX Université de Brest F‐29000 Quimper France
| | - Boumedine Moussa‐Boudjemaa
- Laboratoire de Microbiologie Appliquée à l'Agroalimentaire et à l'Environnement (LAMAABE) Faculté des SNV/STU Université de Tlemcen BP119 13000 Tlemcen Algeria
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Wang N, Sadiq FA, Li S, He G, Yuan L. Tandem mass tag-based quantitative proteomics reveals the regulators in biofilm formation and biofilm control of Bacillus licheniformis. Food Control 2020. [DOI: 10.1016/j.foodcont.2019.107029] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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18
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Dettling A, Doll E, Wedel C, Hinrichs J, Scherer S, Wenning M. Accurate quantification of thermophilic spores in dairy powders. Int Dairy J 2019. [DOI: 10.1016/j.idairyj.2019.07.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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19
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Importance of Individual Germination Receptor Subunits in the Cooperative Function between GerA and Ynd. J Bacteriol 2019; 201:JB.00451-19. [PMID: 31427390 DOI: 10.1128/jb.00451-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 08/06/2019] [Indexed: 11/20/2022] Open
Abstract
Germination of Bacillus spores is triggered by the binding of specific nutrients to germinant receptors (GRs) located in the spore's inner membrane. The GRs typically consist of A, B, and C subunits, encoded by tricistronic ger operons. The Bacillus licheniformis genome contains the gerA family operons gerA, ynd, and gerK In contrast to the ABC(D) organization that characterizes gerA operons of many Bacillus species, B. licheniformis genomes contain a pentacistronic ynd operon comprising the yndD, yndE3 , yndE2 , yndF1 , and yndE1 genes encoding A, B, B, C, and B GR subunits, respectively (subscripts indicate paralogs). Here we show that B. licheniformis spores can germinate in the absence of the Ynd and GerK GRs, although cooperation between all three GRs is required for optimal germination with amino acids. Spores carrying an incomplete set of Ynd B subunits demonstrated reduced germination efficiencies, while depletion of all three Ynd B subunits restored germination of the spore population to levels only slightly lower than those of wild-type spores at high germinant concentrations. This suggests that the presence of an incomplete set of Ynd B subunits exhibits a dominant negative effect on germination and that the A and C subunits of the Ynd GR are sufficient for the cooperative functionality between Ynd and GerA. In contrast to the B subunits of Ynd, the B subunit of GerA was essential for amino acid-induced germination. This study provides novel insights into the role of individual GR subunits in the cooperative interaction between GRs in triggering spore germination.IMPORTANCE Spore-forming bacteria are problematic for the food industry, as spores can survive decontamination procedures and subsequently revive in food products, with the risk of food spoilage and foodborne disease. The Ynd and GerA germination receptors (GRs) cooperate in triggering efficient germination of Bacillus licheniformis spores when nutrients are present in the surrounding environment. This study shows that the single B subunit of GerA is essential for the cooperative function between Ynd and GerA, while the three B subunits of the Ynd GR are dispensable. The ability of GRs lacking individual subunits to stimulate germination together with other GRs could explain why ger operons lacking GR subunit genes are maintained in genomes of spore-forming species.
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Li F, Hunt K, Van Hoorde K, Butler F, Jordan K, Tobin JT. Occurrence and identification of spore-forming bacteria in skim-milk powders. Int Dairy J 2019. [DOI: 10.1016/j.idairyj.2019.05.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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21
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Mehta DS, Metzger LE, Hassan AN, Nelson BK, Patel HA. The ability of spore formers to degrade milk proteins, fat, phospholipids, common stabilizers, and exopolysaccharides. J Dairy Sci 2019; 102:10799-10813. [PMID: 31521346 DOI: 10.3168/jds.2019-16623] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 07/25/2019] [Indexed: 11/19/2022]
Abstract
Spore formers are common spoilage-causing microorganisms in dairy products; however, their modes of spoilage (proteolysis, lipolysis, etc.) have not been described in detail for cultured dairy products such as sour cream and yogurt. The objective of the present study was to test the ability of spore-forming strains isolated from dairy environments for their spoilage-causing activities at typical sour cream (24°C) and yogurt (42°C) fermentation temperatures. A total of 25 spore-forming strains were isolated from different sources, including raw milk, pasteurizer balance tank, biofilms formed on heat exchangers, and milk powder. These strains were tested for proteolytic and lipolytic activities and for their ability to degrade phospholipids, common stabilizers (starch, gelatin, xanthan gum, pectin), and exopolysaccharides (EPS) at sour cream and yogurt fermentation temperatures. A higher percentage of positive strains was observed for selected activities at yogurt fermentation temperature compared with sour cream fermentation temperature. Identified proteolytic spore-forming strains, based on a skim milk agar method, were subsequently quantified for their level of proteolysis using non-casein nitrogen (NCN) content and sodium dodecyl sulfate-PAGE (SDS-PAGE). The proteolytic strains that showed the highest levels of proteolysis (highest percentages of NCN content) at 24°C were Bacillus mojavensis BC, Bacillus cereus DBC, Bacillus subtilis DBC, B. mojavensis DBC1, and Paenibacillus polymyxa DBC1. At 42°C the strains with the highest levels of proteolysis (highest percentages of NCN content) were B. subtilis DBC, B. mojavensis BC, B. mojavensis DBC1, B. cereus DBC, and Bacillus licheniformis DBC6. Results of SDS-PAGE demonstrated that proteolytic strains had primarily hydrolyzed β- and κ-CN. A viscometric method was used to evaluate the susceptibility of exopolysaccharides (EPS) to degradation by selected spore formers. This method helped to determine that EPS produced by commercial yogurt and sour cream cultures is susceptible to degradation by spore formers present in dairy environments.
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Affiliation(s)
- D S Mehta
- Midwest Dairy Foods Research Center, Dairy and Food Science Department, South Dakota State University, Brookings 57007; Research and Development, Wells Enterprises Inc., Le Mars, IA 51031
| | - L E Metzger
- Midwest Dairy Foods Research Center, Dairy and Food Science Department, South Dakota State University, Brookings 57007.
| | - A N Hassan
- Midwest Dairy Foods Research Center, Dairy and Food Science Department, South Dakota State University, Brookings 57007; Daisy Brand, Garland, TX 75041
| | | | - H A Patel
- Midwest Dairy Foods Research Center, Dairy and Food Science Department, South Dakota State University, Brookings 57007; Dairy Foods Research and Development, Land O'Lakes Inc., Arden Hills, MN 55126
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22
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Heat resistance of spores of 18 strains of Geobacillus stearothermophilus and impact of culturing conditions. Int J Food Microbiol 2019; 291:161-172. [DOI: 10.1016/j.ijfoodmicro.2018.11.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 10/14/2018] [Accepted: 11/06/2018] [Indexed: 11/24/2022]
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23
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Griep ER, Cheng Y, Moraru CI. Efficient removal of spores from skim milk using cold microfiltration: Spore size and surface property considerations. J Dairy Sci 2018; 101:9703-9713. [DOI: 10.3168/jds.2018-14888] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 06/28/2018] [Indexed: 02/03/2023]
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24
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Microbiota of milk powders and the heat resistance and spoilage potential of aerobic spore-forming bacteria. Int Dairy J 2018. [DOI: 10.1016/j.idairyj.2018.06.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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25
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Pereira APM, Sant’Ana AS. Diversity and fate of spore forming bacteria in cocoa powder, milk powder, starch and sugar during processing: A review. Trends Food Sci Technol 2018. [DOI: 10.1016/j.tifs.2018.04.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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26
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Propensity for biofilm formation by aerobic mesophilic and thermophilic spore forming bacteria isolated from Chinese milk powders. Int J Food Microbiol 2017; 262:89-98. [DOI: 10.1016/j.ijfoodmicro.2017.09.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 07/27/2017] [Accepted: 09/24/2017] [Indexed: 02/08/2023]
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27
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André S, Vallaeys T, Planchon S. Spore-forming bacteria responsible for food spoilage. Res Microbiol 2017; 168:379-387. [DOI: 10.1016/j.resmic.2016.10.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Revised: 09/30/2016] [Accepted: 10/17/2016] [Indexed: 10/20/2022]
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28
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Ribeiro MC, da Silva Fernandes M, Yoshiteru Kuaye A, Jimenez-Flores R, Gigante M. Preconditioning of the stainless steel surface affects the adhesion of Bacillus cereus spores. Int Dairy J 2017. [DOI: 10.1016/j.idairyj.2016.11.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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29
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McHugh AJ, Feehily C, Hill C, Cotter PD. Detection and Enumeration of Spore-Forming Bacteria in Powdered Dairy Products. Front Microbiol 2017; 8:109. [PMID: 28197144 PMCID: PMC5281614 DOI: 10.3389/fmicb.2017.00109] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 01/16/2017] [Indexed: 01/28/2023] Open
Abstract
With the abolition of milk quotas in the European Union in 2015, several member states including Ireland, Luxembourg, and Belgium have seen year on year bi-monthly milk deliveries to dairies increase by up to 35%. Milk production has also increased outside of Europe in the past number of years. Unsurprisingly, there has been a corresponding increased focus on the production of dried milk products for improved shelf life. These powders are used in a wide variety of products, including confectionery, infant formula, sports dietary supplements and supplements for health recovery. To ensure quality and safety standards in the dairy sector, strict controls are in place with respect to the acceptable quantity and species of microorganisms present in these products. A particular emphasis on spore-forming bacteria is necessary due to their inherent ability to survive extreme processing conditions. Traditional microbiological detection methods used in industry have limitations in terms of time, efficiency, accuracy, and sensitivity. The following review will explore the common spore-forming bacterial contaminants of milk powders, will review the guidelines with respect to the acceptable limits of these microorganisms and will provide an insight into recent advances in methods for detecting these microbes. The various advantages and limitations with respect to the application of these diagnostics approaches for dairy food will be provided. It is anticipated that the optimization and application of these methods in appropriate ways can ensure that the enhanced pressures associated with increased production will not result in any lessening of safety and quality standards.
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Affiliation(s)
- Aoife J McHugh
- Food Bioscience Department, Teagasc Food Research CentreCork, Ireland; School of Microbiology, University College CorkCork, Ireland
| | - Conor Feehily
- Food Bioscience Department, Teagasc Food Research CentreCork, Ireland; APC Microbiome InstituteCork, Ireland
| | - Colin Hill
- School of Microbiology, University College CorkCork, Ireland; APC Microbiome InstituteCork, Ireland
| | - Paul D Cotter
- Food Bioscience Department, Teagasc Food Research CentreCork, Ireland; APC Microbiome InstituteCork, Ireland
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30
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Murphy SC, Martin NH, Barbano DM, Wiedmann M. Influence of raw milk quality on processed dairy products: How do raw milk quality test results relate to product quality and yield? J Dairy Sci 2016; 99:10128-10149. [DOI: 10.3168/jds.2016-11172] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 08/03/2016] [Indexed: 11/19/2022]
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31
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Borch-Pedersen K, Lindbäck T, Madslien EH, Kidd SW, O'Sullivan K, Granum PE, Aspholm M. The Cooperative and Interdependent Roles of GerA, GerK, and Ynd in Germination of Bacillus licheniformis Spores. Appl Environ Microbiol 2016; 82:4279-4287. [PMID: 27208128 PMCID: PMC4959183 DOI: 10.1128/aem.00594-16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 05/01/2016] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED When nutrients are scarce, Bacillus species form metabolically dormant and extremely resistant spores that enable survival over long periods of time under conditions not permitting growth. The presence of specific nutrients triggers spore germination through interaction with germinant receptors located in the spore's inner membrane. Bacillus licheniformis is a biotechnologically important species, but it is also associated with food spoilage and food-borne disease. The B. licheniformis ATCC 14580/DSM13 genome exhibits three gerA family operons (gerA, gerK, and ynd) encoding germinant receptors. We show that spores of B. licheniformis germinate efficiently in response to a range of different single l-amino acid germinants, in addition to a weak germination response seen with d-glucose. Mutational analyses revealed that the GerA and Ynd germination receptors function cooperatively in triggering an efficient germination response with single l-amino acid germinants, whereas the GerK germination receptor is essential for germination with d-glucose. Mutant spores expressing only GerA and GerK or only Ynd and GerK show reduced or severely impaired germination responses, respectively, with single l-amino acid germinants. Neither GerA nor Ynd could function alone in stimulating spore germination. Together, these results functionally characterize the germination receptor operons present in B. licheniformis We demonstrate the overlapping germinant recognition patterns of the GerA and Ynd germination receptors and the cooperative functionalities between GerA, Ynd, and GerK in inducing germination. IMPORTANCE To ensure safe food production and durable foods, there is an obvious need for more knowledge on spore-forming bacteria. It is the process of spore germination that ultimately leads to food spoilage and food poisoning. Bacillus licheniformis is a biotechnologically important species that is also associated with food spoilage and food-borne disease. Despite its importance, the mechanisms of spore germination are poorly characterized in this species. This study provides novel knowledge on germination of B. licheniformis spores. We characterize the germinant recognition profiles of the three germinant receptors present in B. licheniformis spores and demonstrate that the GerA germinant receptor cooperates with the Ynd and GerK germinant receptors to enable an effective germination response to l-amino acids. We also demonstrate that GerK is required for germination in response to the single germinant glucose. This study demonstrates the complex interactions between germinant receptors necessary for efficient germination of B. licheniformis spores.
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Affiliation(s)
- Kristina Borch-Pedersen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Toril Lindbäck
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Elisabeth H Madslien
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
- Forsvarets Forskningsinstitutt FFI, Norwegian Defence Research Establishment, Kjeller, Norway
| | - Shani W Kidd
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Kristin O'Sullivan
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Per Einar Granum
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Marina Aspholm
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
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Kent D, Chauhan K, Boor K, Wiedmann M, Martin N. Spore test parameters matter: Mesophilic and thermophilic spore counts detected in raw milk and dairy powders differ significantly by test method. J Dairy Sci 2016; 99:5180-5191. [DOI: 10.3168/jds.2015-10283] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 03/04/2016] [Indexed: 11/19/2022]
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33
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Characterization of Environmental Bacillus Isolates by Protein Fingerprinting and Random Amplified Polymorphic DNA Profiles. ACTA ACUST UNITED AC 2016. [DOI: 10.1007/s40011-015-0700-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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34
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Gopal N, Hill C, Ross PR, Beresford TP, Fenelon MA, Cotter PD. The Prevalence and Control of Bacillus and Related Spore-Forming Bacteria in the Dairy Industry. Front Microbiol 2015; 6:1418. [PMID: 26733963 PMCID: PMC4685140 DOI: 10.3389/fmicb.2015.01418] [Citation(s) in RCA: 147] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 11/30/2015] [Indexed: 01/14/2023] Open
Abstract
Milk produced in udder cells is sterile but due to its high nutrient content, it can be a good growth substrate for contaminating bacteria. The quality of milk is monitored via somatic cell counts and total bacterial counts, with prescribed regulatory limits to ensure quality and safety. Bacterial contaminants can cause disease, or spoilage of milk and its secondary products. Aerobic spore-forming bacteria, such as those from the genera Sporosarcina, Paenisporosarcina, Brevibacillus, Paenibacillus, Geobacillus and Bacillus, are a particular concern in this regard as they are able to survive industrial pasteurization and form biofilms within pipes and stainless steel equipment. These single or multiple-species biofilms become a reservoir of spoilage microorganisms and a cycle of contamination can be initiated. Indeed, previous studies have highlighted that these microorganisms are highly prevalent in dead ends, corners, cracks, crevices, gaskets, valves and the joints of stainless steel equipment used in the dairy manufacturing plants. Hence, adequate monitoring and control measures are essential to prevent spoilage and ensure consumer safety. Common controlling approaches include specific cleaning-in-place processes, chemical and biological biocides and other novel methods. In this review, we highlight the problems caused by these microorganisms, and discuss issues relating to their prevalence, monitoring thereof and control with respect to the dairy industry.
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Affiliation(s)
- Nidhi Gopal
- Teagasc Food Research CentreCork, Ireland
- School of Microbiology, University College CorkCork, Ireland
| | - Colin Hill
- School of Microbiology, University College CorkCork, Ireland
- APC Microbiome InstituteCork, Ireland
| | - Paul R. Ross
- College of Science, Engineering and Food Science, University College CorkCork, Ireland
| | | | | | - Paul D. Cotter
- Teagasc Food Research CentreCork, Ireland
- APC Microbiome InstituteCork, Ireland
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35
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Miller RA, Kent DJ, Watterson MJ, Boor KJ, Martin NH, Wiedmann M. Spore populations among bulk tank raw milk and dairy powders are significantly different. J Dairy Sci 2015; 98:8492-504. [DOI: 10.3168/jds.2015-9943] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/20/2015] [Indexed: 11/19/2022]
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36
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Sadiq FA, Li Y, Liu T, Flint S, Zhang G, He G. A RAPD based study revealing a previously unreported wide range of mesophilic and thermophilic spore formers associated with milk powders in China. Int J Food Microbiol 2015; 217:200-8. [PMID: 26555161 DOI: 10.1016/j.ijfoodmicro.2015.10.030] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 10/03/2015] [Accepted: 10/31/2015] [Indexed: 11/26/2022]
Abstract
Aerobic spore forming bacteria are potential milk powder contaminants and are viewed as indicators of poor quality. A total of 738 bacteria, including both mesophilic and thermophilic, isolated from twenty-five powdered milk samples representative of three types of milk powders in China were analyzed based on the random amplified polymorphic DNA (RAPD) protocol to provide insight into species diversity. Bacillus licheniformis was found to be the most prevalent bacterium with greatest diversity (~43% of the total isolates) followed by Geobacillus stearothermophilus (~21% of the total isolates). Anoxybacillus flavithermus represented only 8.5% of the total profiles. Interestingly, actinomycetes represented a major group of the isolates with the predominance of Laceyella sacchari followed by Thermoactinomyces vulgaris, altogether comprising of 7.3% of the total isolates. Out of the nineteen separate bacterial species (except five unidentified groups) recovered and identified from milk powders, twelve proved to belong to novel or previously unreported species in milk powders. Assessment and characterization of the harmful effects caused by this particular micro-flora on the quality and safety of milk powders will be worth doing in the future.
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Affiliation(s)
- Faizan A Sadiq
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Yun Li
- Department of Biology, Hanshan Normal University, Chaozhou 521041, China
| | - TongJie Liu
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Steve Flint
- School of Food and Nutrition, Massey University, Private Bag 11 222, Palmerston-North, New Zealand
| | - Guohua Zhang
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - GuoQing He
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
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37
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Nakano M. Development of a Quantitative PCR Assay for Thermophilic Spore-Forming Geobacillus stearothermophilus in Canned Food. Biocontrol Sci 2015; 20:221-7. [PMID: 26412704 DOI: 10.4265/bio.20.221] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
The thermophilic spore forming bacteria Geobacillus stearothermophilus is recognized as a major cause of spoilage in canned food. A quantitative real-time PCR assay was developed to specifically detect and quantify the species G. stearothermophilus in samples from canned food. The selected primer pairs amplified a 163-bp fragment of the 16S rRNA gene in a specific PCR assay with a detection limit of 12.5 fg of pure culture DNA, corresponding to DNA extracted from approximately 0.7 CFU/mL of G. stearothermophilus. Analysis showed that the bacterial species G. stearothermophilus was not detected in any canned food sample. Our approach presented here will be useful for tracking or quantifying species G. stearotethermophilus in canned food and ingredients.
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Affiliation(s)
- Miyo Nakano
- Division of Food Science, Toyo Institute of Food Technology
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38
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Miller R, Kent D, Boor K, Martin N, Wiedmann M. Different management practices are associated with mesophilic and thermophilic spore levels in bulk tank raw milk. J Dairy Sci 2015; 98:4338-51. [DOI: 10.3168/jds.2015-9406] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 03/30/2015] [Indexed: 11/19/2022]
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39
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Nakano M. Detection and Quantification of Thermophilic Spore-Forming Moorella thermoacetica in Canned Beverages Using Real-Time PCR. J Food Prot 2015; 78:1392-6. [PMID: 26197294 DOI: 10.4315/0362-028x.jfp-14-547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A quantitative real-time PCR assay was developed to specifically detect and quantify Moorella thermoacetica and/or Moorella thermoautotrophica from canned coffee beverages. Six different combinations of newly designed primers were examined, and primer pair v1-1F/v4R was found to specifically amplify M. thermoacetica and M. thermoautotrophica. The minimum detection sensitivity was 15 fg of pure culture DNA from M. thermoacetica. Twenty commercial canned coffee beverages were then screened for the presence of M. thermoacetica, and two were shown to contain >1.3 and >1.0 CFU/ml, respectively. Therefore, the assay developed in this study may be useful for accurately tracking and quantifying M. thermoacetica and M. thermoautotrophica in beverage samples.
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Affiliation(s)
- Miyo Nakano
- Division of Food Science, Toyo Institute of Food Technology, 23-2, 4-chome, Minami-hanayashiki, Kawanishi, Hyogo 666-0026, Japan.
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40
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Trmčić A, Martin NH, Boor KJ, Wiedmann M. A standard bacterial isolate set for research on contemporary dairy spoilage. J Dairy Sci 2015; 98:5806-17. [PMID: 26026752 DOI: 10.3168/jds.2015-9490] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 04/11/2015] [Indexed: 11/19/2022]
Abstract
Food spoilage is an ongoing issue that could be dealt with more efficiently if some standardization and unification was introduced in this field of research. For example, research and development efforts to understand and reduce food spoilage can greatly be enhanced through availability and use of standardized isolate sets. To address this critical issue, we have assembled a standard isolate set of dairy spoilers and other selected nonpathogenic organisms frequently associated with dairy products. This publicly available bacterial set consists of (1) 35 gram-positive isolates including 9 Bacillus and 15 Paenibacillus isolates and (2) 16 gram-negative isolates including 4 Pseudomonas and 8 coliform isolates. The set includes isolates obtained from samples of pasteurized milk (n=43), pasteurized chocolate milk (n=1), raw milk (n=1), cheese (n=2), as well as isolates obtained from samples obtained from dairy-powder production (n=4). Analysis of growth characteristics in skim milk broth identified 16 gram-positive and 13 gram-negative isolates as psychrotolerant. Additional phenotypic characterization of isolates included testing for activity of β-galactosidase and lipolytic and proteolytic enzymes. All groups of isolates included in the isolate set exhibited diversity in growth and enzyme activity. Source data for all isolates in this isolate set are publicly available in the FoodMicrobeTracker database (http://www.foodmicrobetracker.com), which allows for continuous updating of information and advancement of knowledge on dairy-spoilage representatives included in this isolate set. This isolate set along with publicly available isolate data provide a unique resource that will help advance knowledge of dairy-spoilage organisms as well as aid industry in development and validation of new control strategies.
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Affiliation(s)
- A Trmčić
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14850
| | - N H Martin
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14850
| | - K J Boor
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14850
| | - M Wiedmann
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14850.
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41
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Buehner KP, Anand S, Djira GD. Prevalence of thermoduric bacteria and spores in nonfat dry milk powders of Midwest origin. J Dairy Sci 2015; 98:2861-6. [DOI: 10.3168/jds.2014-8822] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 01/10/2015] [Indexed: 11/19/2022]
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42
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Durand L, Planchon S, Guinebretiere MH, Carlin F, Remize F. Genotypic and phenotypic characterization of foodborne Geobacillus stearothermophilus. Food Microbiol 2015; 45:103-10. [DOI: 10.1016/j.fm.2014.01.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2013] [Revised: 01/23/2014] [Accepted: 01/27/2014] [Indexed: 11/29/2022]
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43
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Buehner KP, Anand S, Djira GD, Garcia A. Corrigendum to “Prevalence of thermoduric bacteria and spores on 10 Midwest dairy farms”. J Dairy Sci 2014; 97:8009-16. [DOI: 10.3168/jds.2014-97-12-8009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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44
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Chauhan K, Seale RB, Deeth HC, Turner MS. Hypervariable pili and flagella genes provide suitable new targets for DNA high-resolution melt-based genotyping of dairy Geobacillus spp. J Food Prot 2014; 77:1715-22. [PMID: 25285488 DOI: 10.4315/0362-028x.jfp-14-115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Although nonpathogenic in nature, spores of Geobacillus are able to attach to surfaces, germinate, and form biofilms, allowing rapid multiplication and persistence within milk powder processing plants, causing final product contamination, and eventually leading to a loss of revenue in terms of downgraded product quality. As a result, Geobacillus spp. have been found to be common contaminants of milk powder worldwide. Genotyping methods can help in gaining insight into the ecology and transmission of these thermophilic bacteria within and between dairy processing plants. The objective of this study was to use the assembled draft genomes of two Geobacillus spp. to identify and test new hypervariable genotyping targets for differentiating closely related dairy Geobacillus isolates. The two Geobacillus spp. strains obtained from high spore count powders were obtained in 2010 (isolate 7E) and in 1995 (isolate 126) and were previously shown to be of same genotype based on a variable number tandem repeat genotyping method. Significant nucleotide sequence variation was found in genes encoding pili and flagella, which were further investigated as suitable loci for a new high-resolution melt analysis (HRMA)-based genotyping method. Three genes encoding pulG (containing prepilin-type N-terminal cleavage domain), pilT (pili retraction protein), and fliW (flagellar assembly protein) were selected as targets for the new pili/flagella gene (PilFla) HRMA genotyping method. The three-gene-based PilFla-HRMA genotyping method differentiated 35 milk powder Geobacillus spp. isolates into 19 different genotype groups (D = 0.93), which compared favorably to the previous method (which used four variable number tandem repeat loci) that generated 16 different genotype groups (D = 0.90). In conclusion, through comparative genomics of two closely related dairy Geobacillus strains, we have identified new hypervariable regions that prove to be useful targets for highly discriminatory genotyping.
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Affiliation(s)
- Kanika Chauhan
- School of Agriculture and Food Sciences, The University of Queensland, St. Lucia Campus, Brisbane, Queensland 4072, Australia
| | - R Brent Seale
- School of Agriculture and Food Sciences, Auckland University of Technology, City Campus, Auckland 1010, New Zealand
| | - Hilton C Deeth
- School of Agriculture and Food Sciences, The University of Queensland, St. Lucia Campus, Brisbane, Queensland 4072, Australia
| | - Mark S Turner
- School of Agriculture and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia Campus, Brisbane, Queensland 4072, Australia.
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45
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Mondal A, Buchanan RL, Lo YM. Computational fluid dynamics approaches in quality and hygienic production of semisolid low-moisture foods: a review of critical factors. J Food Sci 2014; 79:R1861-70. [PMID: 25224872 DOI: 10.1111/1750-3841.12648] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 07/21/2014] [Indexed: 11/26/2022]
Abstract
Low-moisture foods have been responsible for a number of salmonellosis outbreaks worldwide over the last few decades, with cross contamination from contaminated equipment being the most predominant source. To date, actions have been focused on stringent hygienic practices prior to production, namely periodical sanitization of the processing equipment and lines. Not only does optimum sanitization require in-depth knowledge on the type and source of contaminants, but also the heat resistance of microorganisms is unique and often dependent on the heat transfer characteristics of the low-moisture foods. Rheological properties, including viscosity, degree of turbulence, and flow characteristics (for example, Newtonian or non-Newtonian) of both liquid and semisolid foods are critical factors impacting the flow behavior that consequently interferes heat transfer and related control elements. The demand for progressively more accurate prediction of complex fluid phenomena has called for the employment of computational fluid dynamics (CFD) to model mass and heat transfer during processing of various food products, ranging from drying to baking. With the aim of improving the quality and safety of low-moisture foods, this article critically reviewed the published literature concerning microbial survival in semisolid low-moisture foods, including chocolate, honey, and peanut butter. Critical rheological properties and state-of-the-art CFD application relevant to quality production of those products were also addressed. It is anticipated that adequate prediction of specific transport properties during optimum sanitization through CFD could be used to solve current and future food safety challenges.
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Affiliation(s)
- Arpita Mondal
- Dept. of Nutrition and Food Science, Univ. of Maryland, College Park, MD, 20742, U.S.A
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46
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Buehner KP, Anand S, Djira GD, Garcia A. Prevalence of thermoduric bacteria and spores on 10 Midwest dairy farms. J Dairy Sci 2014; 97:6777-84. [PMID: 25200773 DOI: 10.3168/jds.2014-8342] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 08/06/2014] [Indexed: 11/19/2022]
Abstract
Thermoduric bacteria (TDB), including sporeformers and their spores, can be present in milk and dairy products even after pasteurization. They have the potential to adversely affect the quality and shelf life of products. The objectives of this study were to identify the origin and common species of heat-resistant bacteria occurring during summer and winter on Midwest dairy farms. Bulk tank milk samples were taken from 10 dairy farms located along the South Dakota section of Interstate 29, with herd sizes ranging from 650 to 3,500 lactating dairy cows. Milk samples were profiled for the prevalence of TDB and spore counts (SC). Corn silage samples and swabs of the milking clusters were also taken at the dairies to further profile the potential sources of TDB and SC. The samples were taken 3 times during 2 seasons [winter (January-March) and summer (June-August)] to track seasonal changes in the farm bacterial flora. During winter, the average TDB counts in bulk tank milk were 2.61 log compared with 2.76 log TDB counts in the summer. The SC was 1.08 log in the winter, which was half the 2.06 log SC present in the summer season. Corn silage sampled in winter contained a 7.57 log TDB count compared with an increased 10.77 log TDB count during summer sampling. Concentrations of SC in corn silage reached an average of 6.3 log in winter compared with 11.81 log for summer. The seasonal effect was evident with an increase in summer counts across the board for TDB and SC, both in the feed and bulk tank milk samples. Bacillus licheniformis was the predominant species identified in 62.4% of winter (85 total) and 49.4% of summer (83 total) samples. Bacillus subtilis made up 9.4% of the remaining winter isolates, followed by Bacillus sonorensis at 8.2%. Conversely, B. sonorensis made up 12% of the summer isolates followed by Bacillus pumilus at 10.8%. Bacillus licheniformis is a ubiquitous microbe and was isolated from both TDB and sporeformer categories in all 3 sample types. There were larger increases in SC than TDB, indicating that summer temperatures and conditions may favor proliferation of sporeforming bacteria over that of TDB. In conclusion, samples from bulk tank milk, milking cluster swabs, and corn silage samples at each of the 10 sites indicated that B. licheniformis was the major contaminant species, regardless of season. In this experiment, corn silage was the major environmental source of both TDB and SC with higher concentrations in summer when compared with winter.
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Affiliation(s)
- Kimberly P Buehner
- Midwest Dairy Foods Research Center, Dairy Science Department, South Dakota State University, Brookings 57007
| | - Sanjeev Anand
- Midwest Dairy Foods Research Center, Dairy Science Department, South Dakota State University, Brookings 57007.
| | - Gemechis D Djira
- Department of Mathematics and Statistics, South Dakota State University, Brookings 57007
| | - Alvaro Garcia
- Midwest Dairy Foods Research Center, Dairy Science Department, South Dakota State University, Brookings 57007
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47
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Development of a Multiplex-PCR assay for the rapid identification of Geobacillus stearothermophilus and Anoxybacillus flavithermus. Food Microbiol 2014; 43:41-9. [PMID: 24929881 DOI: 10.1016/j.fm.2014.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 04/29/2014] [Accepted: 05/02/2014] [Indexed: 11/21/2022]
Abstract
The presence of thermophilic bacilli in dairy products is indicator of poor hygiene. Their rapid detection and identification is fundamental to improve the industrial reactivity in the implementation of corrective and preventive actions. In this study a rapid and reliable identification of Geobacillus stearothermophilus and Anoxybacillus flavithermus was achieved by species-specific PCR assays. Two primer sets, targeting the ITS 16S-23S rRNA region and the rpoB gene sequence of the target species respectively, were employed. Species-specificity of both primer sets was evaluated by using 53 reference strains of DSMZ collection; among them, 13 species of the genus Geobacillus and 15 of the genus Anoxybacillus were represented. Moreover, 99 wild strains and 23 bulk cells collected from 24 infant formula powders gathered from several countries worldwide were included in the analyses. Both primer sets were highly specific and the expected PCR fragments were obtained only when DNA from G. stearothermophilus or A. flavithermus was used. After testing their specificity, they were combined in a Multiplex-PCR assay for the simultaneous identification of the two target species. The specificity of the Multiplex-PCR was evaluated by using both wild strains and bulk cells. Every analysis confirmed the reliable identification results provided by the single species-specific PCR methodology. The easiness, the rapidity (about 4 h from DNA isolation to results) and the reliability of the PCR procedures developed in this study highlight the advantage of their application for the specific detection and identification of the thermophilic species G. stearothermophilus and A. flavithermus.
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48
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Draft genome comparison of representatives of the three dominant genotype groups of dairy Bacillus licheniformis strains. Appl Environ Microbiol 2014; 80:3453-62. [PMID: 24657871 DOI: 10.1128/aem.00065-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The spore-forming bacterium Bacillus licheniformis is a common contaminant of milk and milk products. Strains of this species isolated from dairy products can be differentiated into three major groups, namely, G, F1, and F2, using random amplification of polymorphic DNA (RAPD) analysis; however, little is known about the genomic differences between these groups and the identity of the fragments that make up their RAPD profiles. In this work we obtained high-quality draft genomes of representative strains from each of the three RAPD groups (designated strain G-1, strain F1-1, and strain F2-1) and compared them to each other and to B. licheniformis ATCC 14580 and Bacillus subtilis 168. Whole-genome comparison and multilocus sequence typing revealed that strain G-1 contains significant sequence variability and belongs to a lineage distinct from the group F strains. Strain G-1 was found to contain genes coding for a type I restriction modification system, urease production, and bacitracin synthesis, as well as the 8-kbp plasmid pFL7, and these genes were not present in strains F1-1 and F2-1. In agreement with this, all isolates of group G, but no group F isolates, were found to possess urease activity and antimicrobial activity against Micrococcus. Identification of RAPD band sequences revealed that differences in the RAPD profiles were due to differences in gene lengths, 3' ends of predicted primer binding sites, or gene presence or absence. This work provides a greater understanding of the phylogenetic and phenotypic differences observed within the B. licheniformis species.
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49
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Zeigler DR. The Geobacillus paradox: why is a thermophilic bacterial genus so prevalent on a mesophilic planet? Microbiology (Reading) 2014; 160:1-11. [DOI: 10.1099/mic.0.071696-0] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The genus Geobacillus comprises endospore-forming obligate thermophiles. These bacteria have been isolated from cool soils and even cold ocean sediments in anomalously high numbers, given that the ambient temperatures are significantly below their minimum requirement for growth. Geobacilli are active in environments such as hot plant composts, however, and examination of their genome sequences reveals that they are endowed with a battery of sensors, transporters and enzymes dedicated to hydrolysing plant polysaccharides. Although they appear to be relatively minor members of the plant biomass-degrading microbial community, Geobacillus bacteria have achieved a significant population with a worldwide distribution, probably in large part due to adaptive features of their spores. First, their morphology and resistance properties enable them to be mobilized in the atmosphere and transported long distances. Second, their longevity, which in theory may be extreme, enables them to lie quiescent but viable for long periods of time, accumulating gradually over time to achieve surprisingly high population densities.
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Affiliation(s)
- Daniel R. Zeigler
- Department of Microbiology, Ohio State University, 484 W 12th Ave, Columbus, OH 43210, USA
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50
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Lücking G, Stoeckel M, Atamer Z, Hinrichs J, Ehling-Schulz M. Characterization of aerobic spore-forming bacteria associated with industrial dairy processing environments and product spoilage. Int J Food Microbiol 2013; 166:270-9. [DOI: 10.1016/j.ijfoodmicro.2013.07.004] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 07/03/2013] [Accepted: 07/07/2013] [Indexed: 11/30/2022]
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