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Brasca M, Hogenboom JA, Morandi S, Rosi V, D'Incecco P, Silvetti T, Pellegrino L. Proteolytic Activity and Production of γ-Aminobutyric Acid by Streptococcus thermophilus Cultivated in Microfiltered Pasteurized Milk. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:8604-8614. [PMID: 27787997 DOI: 10.1021/acs.jafc.6b03403] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A set of 191 strains of Streptococcus thermophilus were preliminarily screened for the presence of the genes codifying for cell envelope-associated proteinase (prtS) and for glutamate decarboxylase (gadB) responsible for γ-aminobutyric acid (GABA) production. The growth and proteolytic activity of the gadB-positive strains (9 presenting the prtS gene and 11 lacking it) were studied in microfiltered pasteurized milk. Degradation of both caseins (capillary electrophoresis) and soluble nitrogen fractions (HPLC) and changes in the profile of free amino acids (FAAs; ion-exchange chromatography) were evaluated at inoculation and after 6 and 24 h of incubation at 41 °C. None of the strains was capable of hydrolyzing caseins and β-lactoglobulin, and only two hydrolyzed part of α-lactalbumin, these proteins being present in their native states in pasteurized milk. Contrarily, most strains were able to hydrolyze peptones and peptides. For initial growth, most strains relied on the FAAs present in milk, whereas, after 6 h, prtS+ strains released variable amounts of FAA. One prtS+ strain expressed a PrtS- phenotype, and two prtS- strains showed a rather intense proteolytic activity. Only five strains (all prtS+) produced GABA, in variable quantities (up to 100 mg/L) and at different rates, depending on the acidification strength. Addition of glutamate did not induce production of GABA in nonproducing strains that, however, unexpectedly were shown to adopt the degradation of arginine into citrulline and ornithine as an alternative acid resistance system and likely as a source of ATP.
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Affiliation(s)
- Milena Brasca
- Institute of Sciences of Food Production, National Research Council of Italy , Milan, Italy
| | - Johannes A Hogenboom
- Department of Food, Environmental and Nutritional Sciences, University of Milan , Milan, Italy
| | - Stefano Morandi
- Institute of Sciences of Food Production, National Research Council of Italy , Milan, Italy
| | - Veronica Rosi
- Department of Food, Environmental and Nutritional Sciences, University of Milan , Milan, Italy
| | - Paolo D'Incecco
- Department of Food, Environmental and Nutritional Sciences, University of Milan , Milan, Italy
| | - Tiziana Silvetti
- Institute of Sciences of Food Production, National Research Council of Italy , Milan, Italy
| | - Luisa Pellegrino
- Department of Food, Environmental and Nutritional Sciences, University of Milan , Milan, Italy
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Hou JC, Liu F, Ren DX, Han WW, Du YO. Effect of culturing conditions on the expression of key enzymes in the proteolytic system of Lactobacillus bulgaricus. J Zhejiang Univ Sci B 2015; 16:317-26. [PMID: 25845365 DOI: 10.1631/jzus.b1400230] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The proteolytic system of Lactobacillus bulgaricus breaks down milk proteins into peptides and amino acids, which are essential for the growth of the bacteria. The aim of this study was to determine the expressions of seven key genes in the proteolytic system under different culturing conditions (different phases, initial pH values, temperatures, and nitrogen sources) using real-time polymerase chain reaction (RT-PCR). The transcriptions of the seven genes were reduced by 30-fold on average in the stationary phase compared with the exponential growth phase. The transcriptions of the seven genes were reduced by 62.5-, 15.0-, and 59.0-fold in the strains KLDS 08006, KLDS 08007, and KLDS 08012, respectively, indicating that the expressions of the seven genes were significantly different among strains. In addition, the expressions of the seven genes were repressed in the MRS medium containing casein peptone. The effect of peptone supply on PepX transcription was the weakest compared with the other six genes, and the impact on OppD transcription was the strongest. Moreover, the expressions of the seven genes were significantly different among different strains (P<0.05). All these results indicated that the culturing conditions affected the expression of the proteolytic system genes in Lactobacillus bulgaricus at the transcription level.
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Affiliation(s)
- Jun-cai Hou
- Key Laboratory of Dairy Science, Ministry of Education, Northeast Agricultural University, Harbin 150030, China; College of Food Science, Northeast Agricultural University, Harbin 150030, China; College of Animal Sciences, Zhejiang University, Hangzhou 310058, China
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Lu WW, Wang Y, Wang T, Kong J. The global regulator CodY in Streptococcus thermophilus controls the metabolic network for escalating growth in the milk environment. Appl Environ Microbiol 2015; 81:2349-58. [PMID: 25616791 PMCID: PMC4357943 DOI: 10.1128/aem.03361-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 01/15/2015] [Indexed: 02/04/2023] Open
Abstract
CodY is a transcriptional regulator conserved in the low-GC group of Gram-positive bacteria. In this work, we demonstrated the presence in Streptococcus thermophilus ST2017 of a functional member of the CodY family of global regulatory proteins, S. thermophilus CodY (CodYSt). The CodYSt regulon was identified by transcriptome analysis; it consisted predominantly of genes involved in amino acid metabolism but also included genes involved in several other cellular processes, including carbon metabolism, nutrient transport, and stress response. It was revealed that CodYSt repressed the transformation of the central metabolic pathway to amino acid metabolism and improved lactose utilization. Furthermore, the glutamate dehydrogenase gene (gdhA), repressed by CodYSt, was suggested to coordinate the interconversion between carbon metabolism and amino acid metabolism and to play an important role on the optimal growth of S. thermophilus ST2017 in milk. A conserved CodYSt box [AA(T/A)(A/T)TTCTGA(A/C)AATT] was indeed required for in vitro binding of CodYSt to the target regions of DNA. These results provided evidence for the function of CodYSt, by which this strain coordinately regulates its various metabolic pathways so as to adapt to the milk environment.
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Affiliation(s)
- W W Lu
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, People's Republic of China State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, People's Republic of China
| | - Y Wang
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, People's Republic of China
| | - T Wang
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, People's Republic of China
| | - J Kong
- State Key Laboratory of Microbial Technology, Shandong University, Jinan, People's Republic of China
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Bong D, Moraru C. Use of micellar casein concentrate for Greek-style yogurt manufacturing: Effects on processing and product properties. J Dairy Sci 2014; 97:1259-69. [DOI: 10.3168/jds.2013-7488] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Accepted: 11/24/2013] [Indexed: 11/19/2022]
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Abstract
This review describes recent scientific and technological drivers of food fermentation research. In addition, a number of practical implications of the results of this development will be highlighted. The first part of the manuscript elaborates on the message that genome sequence information gives us an unprecedented view on the biodiversity of microbes in food fermentation. This information can be made applicable for tailoring relevant characteristics of food products through fermentation. The second part deals with the integration of genome sequence data into metabolic models and the use of these models for a number of topics that are relevant for food fermentation processes. The final part will be about metagenomics approaches to reveal the complexity and understand the functionality of undefined complex microbial consortia used in a diverse range of food fermentation processes.
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Affiliation(s)
- E J Smid
- NIZO Food Research, 6710 BA Ede, The Netherlands.
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ÖZOĞUL F, KULEY E, ÖZOĞUL Y, ÖZOĞUL İ. The Function of Lactic Acid Bacteria on Biogenic Amines Production by Food-Borne Pathogens in Arginine Decarboxylase Broth. FOOD SCIENCE AND TECHNOLOGY RESEARCH 2012. [DOI: 10.3136/fstr.18.795] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Genome-scale model of Streptococcus thermophilus LMG18311 for metabolic comparison of lactic acid bacteria. Appl Environ Microbiol 2009; 75:3627-33. [PMID: 19346354 DOI: 10.1128/aem.00138-09] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this report, we describe the amino acid metabolism and amino acid dependency of the dairy bacterium Streptococcus thermophilus LMG18311 and compare them with those of two other characterized lactic acid bacteria, Lactococcus lactis and Lactobacillus plantarum. Through the construction of a genome-scale metabolic model of S. thermophilus, the metabolic differences between the three bacteria were visualized by direct projection on a metabolic map. The comparative analysis revealed the minimal amino acid auxotrophy (only histidine and methionine or cysteine) of S. thermophilus LMG18311 and the broad variety of volatiles produced from amino acids compared to the other two bacteria. It also revealed the limited number of pyruvate branches, forcing this strain to use the homofermentative metabolism for growth optimization. In addition, some industrially relevant features could be identified in S. thermophilus, such as the unique pathway for acetaldehyde (yogurt flavor) production and the absence of a complete pentose phosphate pathway.
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Svensson M, Lohmeier-Vogel E, Waak E, Svensson U, Rådström P. Altered nucleotide sugar metabolism in Streptococcus thermophilus interferes with nitrogen metabolism. Int J Food Microbiol 2007; 113:195-200. [PMID: 16996629 DOI: 10.1016/j.ijfoodmicro.2006.06.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 02/24/2006] [Accepted: 06/13/2006] [Indexed: 11/24/2022]
Abstract
Exopolysaccharide (EPS)-producing Streptococcus thermophilus strains have attracted interest recently, since the EPSs act as natural viscosifiers and texture enhancers of fermented foods. We have previously reported that the low level of EPS production by S. thermophilus LY03 could be improved by altering the activities of enzymes in the central carbon metabolism involved in the nucleotide sugar metabolism. In this study, we observed a reduced growth in milk for the strains with increased UDP-glucose pyrophosphorylase (GalU) activity together with either enhanced phosphoglucomutase activity, and/or enhanced activity of the Leloir enzymes. Rapid growth of these mutants in milk could be restored by the addition of four specific amino acids, i.e. Glu, His, Met, and Val. This amino acid requirement was confirmed in a defined medium. Furthermore, the 31P NMR spectra showed higher levels of the GalU reactants pyrophosphate (PPi) and UDP-glucose in the engineered strain, TMB 6013, compared to the parent strain, LY03. These products plus Glu and the GalU reactant UTP are known to be involved in the nitrogen regulatory system in many bacteria. Thus, these results suggest that the reaction catalyzed by GalU is connected to the nitrogen demand of these engineered strains.
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Affiliation(s)
- M Svensson
- Applied Microbiology, Lund Institute of Technology, Lund University, SE-221 00 Lund, Sweden
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Simova E, Simov Z, Beshkova D, Frengova G, Dimitrov Z, Spasov Z. Amino acid profiles of lactic acid bacteria, isolated from kefir grains and kefir starter made from them. Int J Food Microbiol 2006; 107:112-23. [PMID: 16297479 DOI: 10.1016/j.ijfoodmicro.2005.08.020] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2005] [Revised: 06/14/2005] [Accepted: 08/21/2005] [Indexed: 11/25/2022]
Abstract
The characteristics of cell growth, lactic acid production, amino acid release and consumption by single-strain cultures of lactic acid bacteria (isolated from kefir grains), and by a multiple-strain kefir starter prepared from them, were studied. The change in the levels of free amino acids was followed throughout the kefir process: single-strain kefir bacteria and the kefir starter (Lactococcus lactis C15-1%+Lactobacillus helveticus MP12-3%+(Streptococcus thermophilus T15+Lactobacillus bulgaricus HP1 = 1:1)-3%) were cultivated in pasteurized (92 degrees C for 20 min) cow's milk (3% fat content) at 28 degrees C for 5 h (the kefir starter reached pH 4.7) and subsequently grown at 20 degrees C for 16 h; storage was at 4 degrees C for 168 h. The strain L. helveticus MP12 was unrivaled with respect to free amino acid production (53.38 mg (100 g)(-1)) and cell growth (17.8 x 10(8) CFU ml(-1)); however, it manifested the lowest acidification activity. L. bulgaricus HP1 released approximately 3.7 times less amino acids, nearly 5 times lower cell growth, and produced about 1.2 times more lactic acid. S. thermophilus T15 demonstrated dramatically complex amino acid necessities for growth and metabolism. With L. lactis C15, the highest levels of growth and lactic acid synthesis were recorded (18.3 x 10(8) CFU ml(-1) and 7.8 g l(-1) lactic acid at the 21st hour), and as for free amino acid production, it approximated L. bulgaricus HP1 (17.03 mg (100 g)(-1) maximum concentration). In the L. lactis C15 culture, the amino acids were used more actively throughout the first exponential growth phase (by the 10th hour) than during the second growth phase. The unique properties of the L. helveticus MP12 strain to produce amino acids were employed to create a symbiotic bioconsortium kefir culture, which, under conditions of kefir formation, enhanced lactic acid production and shortened the time required to reach pH 4.7; intensified cell growth activity, resulting in a respective 90- and 60-fold increase in the concentration of lactobacilli and cocci in the mixed culture compared to individual cultures; and accumulated free amino acids in the final kefir with higher total concentrations (56.88 mg (100 g)(-1)) and an individual concentration of essential amino acids (1.5 times) greater than that of yogurt.
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Affiliation(s)
- Emilina Simova
- Laboratory of Applied Microbiology, Institute of Microbiology, Bulgarian Academy of Sciences, 26 Maritza Blvd, 4002 Plovdiv, Bulgaria.
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Derzelle S, Bolotin A, Mistou MY, Rul F. Proteome analysis of Streptococcus thermophilus grown in milk reveals pyruvate formate-lyase as the major upregulated protein. Appl Environ Microbiol 2006; 71:8597-605. [PMID: 16332852 PMCID: PMC1317329 DOI: 10.1128/aem.71.12.8597-8605.2005] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the adaptation to milk of Streptococcus thermophilus LMG18311 using a proteomic approach. Two-dimensional electrophoresis of cytosolic proteins were performed after growth in M17 medium or in milk. A major modification of the proteome concerned proteins involved in the supply of amino acids, like the peptidase PepX, and several enzymes involved in amino acid biosynthesis. In parallel, we observed the upregulation of the synthesis of seven enzymes directly involved in the synthesis of purines, as well as formyl-tetrahydrofolate (THF) synthetase and serine hydroxy-methyl transferase, two enzymes responsible for the synthesis of compounds (THF and glycine, respectively) feeding the purine biosynthetic pathway. The analysis also revealed a massive increase in the synthesis of pyruvate formate-lyase (PFL), the enzyme which converts pyruvate into acetyl coenzyme A and formate. PFL has been essentially studied for its role in mixed-acid product formation in lactic acid bacteria during anaerobic fermentation. However, formate is an important methyl group donor for anabolic pathway through the formation of folate derivates. We hypothesized that PFL was involved in purine biosynthesis during growth in milk. We showed that PFL expression was regulated at the transcriptional level and that pfl transcription occurred during the exponential growth phase in milk. The complementation of milk with formate or purine bases was shown to reduce pfl expression, to suppress PFL synthesis, and to stimulate growth of S. thermophilus. These results show a novel regulatory mechanism controlling the synthesis of PFL and suggest an unrecognized physiological role for PFL as a formate supplier for anabolic purposes.
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Affiliation(s)
- Sylviane Derzelle
- Unité Biologie des Bactéries Pathogénes à Gram Positif, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris, France
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Juille O, Bars DL, Juillard V. The specificity of oligopeptide transport by Streptococcus thermophilus resembles that of Lactococcus lactis and not that of pathogenic streptococci. MICROBIOLOGY-SGM 2005; 151:1987-1994. [PMID: 15942005 DOI: 10.1099/mic.0.27730-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Peptide transport is a crucial step in the growth of Streptococcus thermophilus in protein- or peptide-containing media. The objective of the present work was to determine the specificity of peptide utilization by this widely used lactic acid bacterium. To reach that goal, complementary approaches were employed. The capability of a proteinase-negative S. thermophilus strain to grow in a chemically defined medium containing a mixture of peptides isolated from milk as the source of amino acids was analysed. Peptides were separated into three size classes by ultrafiltration. The strain was able to use peptides up to 3.5 kDa during growth, as revealed by liquid chromatography and mass spectrometry analyses. The same strain was grown in chemically defined medium containing a tryptic digest of casein, and the respective time-course consumption of the peptides during growth was estimated. The ability to consume large peptides (up to 23 residues) was confirmed, as long as they are cationic and hydrophobic. These results were confirmed by peptide transport studies. Extension of the study to 11 other strains revealed that they all shared these preferences.
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Affiliation(s)
- Odile Juille
- Unité de Biochimie et Structure des Protéines, Institut National de la Recherche Agronomique, Centre de Recherches de Jouy-en-Josas, 78352 Jouy-en-Josas Cedex, France
| | - Dominique Le Bars
- Unité de Biochimie et Structure des Protéines, Institut National de la Recherche Agronomique, Centre de Recherches de Jouy-en-Josas, 78352 Jouy-en-Josas Cedex, France
| | - Vincent Juillard
- Useful Bacterial Surface Proteins, Unité de Recherches Laitières et Génétique Appliquée, Institut National de la Recherche Agronomique, Centre de Recherches de Jouy-en-Josas, 78352 Jouy-en-Josas Cedex, France
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Hols P, Hancy F, Fontaine L, Grossiord B, Prozzi D, Leblond-Bourget N, Decaris B, Bolotin A, Delorme C, Dusko Ehrlich S, Guédon E, Monnet V, Renault P, Kleerebezem M. New insights in the molecular biology and physiology ofStreptococcus thermophilusrevealed by comparative genomics. FEMS Microbiol Rev 2005. [DOI: 10.1016/j.fmrre.2005.04.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Monnet C, Nardi M, Hols P, Gulea M, Corrieu G, Monnet V. Regulation of branched-chain amino acid biosynthesis by alpha-acetolactate decarboxylase in Streptococcus thermophilus. Lett Appl Microbiol 2003; 36:399-405. [PMID: 12753249 DOI: 10.1046/j.1472-765x.2003.01326.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS To demonstrate the presence of an active alpha-acetolactate decarboxylase in Streptococcus thermophilus and to investigate its physiological function. METHODS AND RESULTS Streptococcus thermophilus CNRZ385 contains a gene encoding an alpha-acetolactate decarboxylase. Comparison of the production of alpha-acetolactate and its decarboxylation products, by the parent strain and an alpha-acetolactate decarboxylase-deficient mutant, demonstrated the presence of a control of the pool of alpha-acetolactate by valine, leucine and isoleucine. This control occurs via an allosteric activation of the alpha-acetolactate decarboxylase. Cell-free extracts of S. thermophilus were not able to decarboxylate the isoleucine precursor alpha-acetohydroxybutyrate. CONCLUSIONS These results strongly suggest that one of the physiological functions of the alpha-acetolactate decarboxylase in S. thermophilus is to regulate leucine and valine biosynthesis by diverting the flux of alpha-acetolactate towards acetoin when the branched-chain amino acids are present at a high concentration. SIGNIFICANCE AND IMPACT OF THE STUDY Regulation of branched-chain amino acid biosynthesis by alpha-acetolactate decarboxylase may occur in several other micro-organisms and explain some of their growth properties.
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Affiliation(s)
- C Monnet
- Unité Mixte de Recherche Génie et Microbiologie des Procés Alimentaires, Institut National de la Recherche Agronomique, Thiverval-Grignon, France.
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Guimont C. Change of free amino acids in M17 medium after growth of Streptococcus thermophilus and identification of a glutamine transport ATP-binding protein. Int Dairy J 2002. [DOI: 10.1016/s0958-6946(02)00068-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Letort C, Juillard V. Development of a minimal chemically-defined medium for the exponential growth of Streptococcus thermophilus. J Appl Microbiol 2001; 91:1023-9. [PMID: 11851809 DOI: 10.1046/j.1365-2672.2001.01469.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS The present work aimed to define a minimal chemically-defined medium which could sustain the growth of most (if not all) strains of Streptococcus thermophilus. METHODS AND RESULTS A minimal medium containing 20 components, including one carbohydrate source, six amino acids, two metallic ions, six vitamins and urea allowed for growth of 13 out of 15 Strep. thermophilus strains. Growth of the two last strains required the presence of additional amino acids, the number of which depended on the strain. Growth rates of the strains in the minimal medium ranged from 0.38 to 0.64 h(-1), and final populations were about 10(8) cfu ml(-1). CONCLUSIONS Streptococcus thermophilus appears much less demanding than other lactic acid bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY The definition of such a growth medium will be very useful for metabolic flux studies as well as peptide transport studies.
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Affiliation(s)
- C Letort
- Unité de Recherches Laitières et Génétique Appliquée, INRA, Jouy-en-Josas, France
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Giraffa G, Paris A, Valcavi L, Gatti M, Neviani E. Genotypic and phenotypic heterogeneity of Streptococcus thermophilus strains isolated from dairy products. J Appl Microbiol 2001; 91:937-43. [PMID: 11722674 DOI: 10.1046/j.1365-2672.2001.01464.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS Forty strains of Streptococcus thermophilus isolated from dairy products were identified and typed by a polyphasic approach which included phenotypic and genotypic criteria. METHODS AND RESULTS Strains were identified by sugar fermentation pattern and species-specific PCR. Phenotypic diversity was evaluated by a chemometric model taking into account some biochemical characteristics (e.g. acidifying and peptidase activities) of technological interest. Genotypic diversity was evidenced by PCR fingerprinting. The overall phenotypic and genotypic information was elaborated on a multivariate statistical basis by principal components analysis and cluster analysis, respectively. When acidifying and peptidase activities were considered, PCA indicated that most of the strains isolated from Pecorino Toscano cheese were separable from the others. Similarly, most of the starter culture strains tended to separate from the cheese isolates. CONCLUSIONS A wide strain heterogeneity among Strep. thermophilus strains isolated from dairy products was observed. SIGNIFICANCE AND IMPACT OF THE STUDY A computerized analysis of genotypic and phenotypic information could be applied successfully to differentiate and characterize reliably and rapidly isolates occurring in different dairy products and to comprehend the technological role of specific Strep. thermophilus strains in dairy technology.
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Affiliation(s)
- G Giraffa
- Department of Microbiology and Enzymology, Istituto Sperimentale Lattiero Caseario, 26900 Lodi, Italy.
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Garault P, Letort C, Juillard V, Monnet V. Branched-chain amino acid biosynthesis is essential for optimal growth of Streptococcus thermophilus in milk. Appl Environ Microbiol 2000; 66:5128-33. [PMID: 11097879 PMCID: PMC92433 DOI: 10.1128/aem.66.12.5128-5133.2000] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lactic acid bacteria are nutritionally demanding bacteria which need, among other things, amino acids for optimal growth. We identified the branched-chain amino acid (BCAA) biosynthesis pathway as an essential pathway for optimal growth of Streptococcus thermophilus in milk. Through random insertional mutagenesis, we isolated and characterized two mutants for which growth in milk is affected as a consequence of ilvB and ilvC gene interruptions. This situation demonstrates that the BCAA biosynthesis pathway is active in S. thermophilus. BCAA biosynthesis is necessary but not sufficient for optimal growth of S. thermophilus and is subject to retro-inhibition processes. The specificity of the BCAA biosynthesis pathway in S. thermophilus lies in the independent transcription of the ilvC gene encoding a keto acid reductoisomerase acting on acetolactate at the junction of the BCAA and acetoin biosynthesis pathways. The possible advantages for S. thermophilus of keeping this biosynthesis pathway active could be linked either to adaptation of the organism to milk, which is different than that of other dairy bacteria, or to the role of the pathway in maintaining the internal pH.
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Affiliation(s)
- P Garault
- Unité de Biochimie et Structure des Protéines, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas Cedex, France
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Fernandez-Espla MD, Garault P, Monnet V, Rul F. Streptococcus thermophilus cell wall-anchored proteinase: release, purification, and biochemical and genetic characterization. Appl Environ Microbiol 2000; 66:4772-8. [PMID: 11055922 PMCID: PMC92378 DOI: 10.1128/aem.66.11.4772-4778.2000] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2000] [Accepted: 08/04/2000] [Indexed: 02/06/2023] Open
Abstract
Streptococcus thermophilus CNRZ 385 expresses a cell envelope proteinase (PrtS), which is characterized in the present work, both at the biochemical and genetic levels. Since PrtS is resistant to most classical methods of extraction from the cell envelopes, we developed a three-step process based on loosening of the cell wall by cultivation of the cells in the presence of glycine (20 mM), mechanical disruption (with alumina powder), and enzymatic treatment (lysozyme). The pure enzyme is a serine proteinase highly activated by Ca(2+) ions. Its activity was optimal at 37 degrees C and pH 7.5 with acetyl-Ala-Ala-Pro-Phe-paranitroanilide as substrate. The study of the hydrolysis of the chromogenic and casein substrates indicated that PrtS presented an intermediate specificity between the most divergent types of cell envelope proteinases from lactococci, known as the PI and PIII types. This result was confirmed by the sequence determination of the regions involved in substrate specificity, which were a mix between those of PI and PIII types, and also had unique residues. Sequence analysis of the PrtS encoding gene revealed that PrtS is a member of the subtilase family. It is a multidomain protein which is maturated and tightly anchored to the cell wall via a mechanism involving an LPXTG motif. PrtS bears similarities to cell envelope proteinases from pyogenic streptococci (C5a peptidase and cell surface proteinase) and lactic acid bacteria (PrtP, PrtH, and PrtB). The highest homologies were found with streptococcal proteinases which lack, as PrtS, one domain (the B domain) present in cell envelope proteinases from all other lactic acid bacteria.
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Affiliation(s)
- M D Fernandez-Espla
- Unité de Recherche de Biochimie et Structure des Protéines, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas Cedex, France
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Grobben GJ, Chin-Joe I, Kitzen VA, Boels IC, Boer F, Sikkema J, Smith MR, de Bont JA. Enhancement of Exopolysaccharide Production by
Lactobacillus delbrueckii
subsp.
bulgaricus
NCFB 2772 with a Simplified Defined Medium. Appl Environ Microbiol 1998; 64:1333-7. [PMID: 16349540 PMCID: PMC106151 DOI: 10.1128/aem.64.4.1333-1337.1998] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ABSTRACT
The aim of this work was to investigate the medium requirements for growth and production of exopolysaccharides by
Lactobacillus delbrueckii
subsp.
bulgaricus
NCFB 2772. The strain was grown in batch cultures on a chemically defined medium, and the technique of single omission of medium components was applied to determine the nutritional requirements. The omission of aspartic acid, glutamic acid, or glycine affected growth only slightly, and the omission of glutamine, asparagine, or threonine resulted in a stronger reduction of the growth. All the other amino acids were essential. Multiple omissions of amino acids caused an almost complete loss of growth.
L. delbrueckii
subsp.
bulgaricus
required only riboflavin, calcium pantothenate, and nicotinic acid as individual vitamins. Surprisingly, when only these vitamins were present in the medium and other vitamins were not, less growth was observed than in the complete medium but the amount of exopolysaccharide produced was significantly greater. These observations were studied in more detail with a simplified defined medium in which
L. delbrueckii
subsp.
bulgaricus
was able to grow and produce exopolysaccharides. Although the final optical density in the simplified medium was lower, the production of exopolysaccharides was about twofold higher than in the complete medium.
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Affiliation(s)
- G J Grobben
- Division of Industrial Microbiology, Department of Food Technology and Nutrition Sciences, Wageningen Agricultural University, 6700 EV Wageningen, Friesland Coberco Dairy Foods, 8901 MA Leeuwarden, and Netherlands Institute for Dairy Research, 6710 BA Ede, The Netherlands
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