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O'Connell LM, Kelleher P, van Rijswijck IMH, de Waal P, van Peij NNME, Mahony J, van Sinderen D. Natural Transformation in Gram-Positive Bacteria and Its Biotechnological Relevance to Lactic Acid Bacteria. Annu Rev Food Sci Technol 2022; 13:409-431. [PMID: 35333592 DOI: 10.1146/annurev-food-052720-011445] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Competence refers to the specialized physiological state in which bacteria undergo transformation through the internalization of exogenous DNA in a controlled and genetically encoded process that leads to genotypic and, in many cases, phenotypic changes. Natural transformation was first described in Streptococcus pneumoniae and has since been demonstrated in numerous species, including Bacillus subtilis and Neisseria gonorrhoeae. Homologs of the genes encoding the DNA uptake machinery for natural transformation have been reported to be present in several lactic acid bacteria, including Lactobacillus spp., Streptococcus thermophilus, and Lactococcus spp. In this review, we collate current knowledge of the phenomenon of natural transformation in Gram-positive bacteria. Furthermore, we describe the mechanism of competence development and its regulation in model bacterial species. We highlight the importance and opportunities for the application of these findings in the context of bacterial starter cultures associated with food fermentations as well as current limitations in this area of research.
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Affiliation(s)
- Laura M O'Connell
- APC Microbiome Ireland and School of Microbiology, University College Cork, Cork, Ireland;
| | - Philip Kelleher
- APC Microbiome Ireland and School of Microbiology, University College Cork, Cork, Ireland;
| | | | - Paul de Waal
- DSM Biotechnology Center, Delft, The Netherlands
| | | | - Jennifer Mahony
- APC Microbiome Ireland and School of Microbiology, University College Cork, Cork, Ireland;
| | - Douwe van Sinderen
- APC Microbiome Ireland and School of Microbiology, University College Cork, Cork, Ireland;
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Glowacki RWP, Pudlo NA, Tuncil Y, Luis AS, Sajjakulnukit P, Terekhov AI, Lyssiotis CA, Hamaker BR, Martens EC. A Ribose-Scavenging System Confers Colonization Fitness on the Human Gut Symbiont Bacteroides thetaiotaomicron in a Diet-Specific Manner. Cell Host Microbe 2019; 27:79-92.e9. [PMID: 31901520 DOI: 10.1016/j.chom.2019.11.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 10/03/2019] [Accepted: 11/18/2019] [Indexed: 12/17/2022]
Abstract
Efficient nutrient acquisition in the human gut is essential for microbial persistence. Although polysaccharides have been well-studied nutrients for the gut microbiome, other resources such as nucleic acids and nucleosides are less studied. We describe several ribose-utilization systems (RUSs) that are broadly represented in Bacteroidetes and appear to have diversified to access ribose from a variety of substrates. One Bacteroides thetaiotaomicron RUS variant is critical for competitive gut colonization in a diet-specific fashion. We used molecular genetics to probe the required functions of the system and the nature of the nutrient source(s) underlying this phenotype. Two RUS-encoded ribokinases were the only components required for this effect, presumably because they generate ribose-phosphate derivatives from products of an unlinked but essential nucleoside phosphorylase. Our results underscore the extensive mechanisms that gut symbionts have evolved to access nutrients and the potential for unexpected dependencies among systems that mediate colonization and persistence.
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Affiliation(s)
- Robert W P Glowacki
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Nicholas A Pudlo
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Yunus Tuncil
- Department of Food Science and Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN 47907, USA
| | - Ana S Luis
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Peter Sajjakulnukit
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Anton I Terekhov
- Department of Food Science and Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN 47907, USA
| | - Costas A Lyssiotis
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Bruce R Hamaker
- Department of Food Science and Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN 47907, USA
| | - Eric C Martens
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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Adaptation of Escherichia coli to Long-Term Serial Passage in Complex Medium: Evidence of Parallel Evolution. mSystems 2017; 2:mSystems00192-16. [PMID: 28289732 PMCID: PMC5340864 DOI: 10.1128/msystems.00192-16] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/03/2017] [Indexed: 11/20/2022] Open
Abstract
With a growing body of work directed toward understanding the mechanisms of evolution using experimental systems, it is crucial to decipher what effects the experimental setup has on the outcome. If the goal of experimental laboratory evolution is to elucidate underlying evolutionary mechanisms and trends, these must be demonstrated in a variety of systems and environments. Here, we perform experimental evolution in a complex medium allowing the cells to transition through all five phases of growth, including death phase and long-term stationary phase. We show that the swiftness of selection and the specific targets of adaptive evolution are different in this system compared to others. We also observe parallel evolution where different mutations in the same genes are under positive natural selection. Together, these data show that while some outcomes of microbial evolution experiments may be generalizable, many outcomes will be environment or system specific. Experimental evolution of bacterial populations in the laboratory has led to identification of several themes, including parallel evolution of populations adapting to carbon starvation, heat stress, and pH stress. However, most of these experiments study growth in defined and/or constant environments. We hypothesized that while there would likely continue to be parallelism in more complex and changing environments, there would also be more variation in what types of mutations would benefit the cells. In order to test our hypothesis, we serially passaged Escherichia coli in a complex medium (Luria-Bertani broth) throughout the five phases of bacterial growth. This passaging scheme allowed cells to experience a wide variety of stresses, including nutrient limitation, oxidative stress, and pH variation, and therefore allowed them to adapt to several conditions. After every ~30 generations of growth, for a total of ~300 generations, we compared both the growth phenotypes and genotypes of aged populations to the parent population. After as few as 30 generations, populations exhibit changes in growth phenotype and accumulate potentially adaptive mutations. There were many genes with mutant alleles in different populations, indicating potential parallel evolution. We examined 8 of these alleles by constructing the point mutations in the parental genetic background and competed those cells with the parent population; five of these alleles were found to be adaptive. The variety and swiftness of adaptive mutations arising in the populations indicate that the cells are adapting to a complex set of stresses, while the parallel nature of several of the mutations indicates that this behavior may be generalized to bacterial evolution. IMPORTANCE With a growing body of work directed toward understanding the mechanisms of evolution using experimental systems, it is crucial to decipher what effects the experimental setup has on the outcome. If the goal of experimental laboratory evolution is to elucidate underlying evolutionary mechanisms and trends, these must be demonstrated in a variety of systems and environments. Here, we perform experimental evolution in a complex medium allowing the cells to transition through all five phases of growth, including death phase and long-term stationary phase. We show that the swiftness of selection and the specific targets of adaptive evolution are different in this system compared to others. We also observe parallel evolution where different mutations in the same genes are under positive natural selection. Together, these data show that while some outcomes of microbial evolution experiments may be generalizable, many outcomes will be environment or system specific.
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Yamamoto T, Kida Y, Sakamoto Y, Kuwano K. Mpn491, a secreted nuclease ofMycoplasma pneumoniae, plays a critical role in evading killing by neutrophil extracellular traps. Cell Microbiol 2016; 19. [DOI: 10.1111/cmi.12666] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 08/30/2016] [Accepted: 08/31/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Takeshi Yamamoto
- Division of Microbiology, Department of Infectious Medicine; Kurume University School of Medicine; Kurume 830-0011 Japan
| | - Yutaka Kida
- Division of Microbiology, Department of Infectious Medicine; Kurume University School of Medicine; Kurume 830-0011 Japan
| | - Yuichi Sakamoto
- Division of Microbiology, Department of Infectious Medicine; Kurume University School of Medicine; Kurume 830-0011 Japan
| | - Koichi Kuwano
- Division of Microbiology, Department of Infectious Medicine; Kurume University School of Medicine; Kurume 830-0011 Japan
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Tran TM, MacIntyre A, Hawes M, Allen C. Escaping Underground Nets: Extracellular DNases Degrade Plant Extracellular Traps and Contribute to Virulence of the Plant Pathogenic Bacterium Ralstonia solanacearum. PLoS Pathog 2016; 12:e1005686. [PMID: 27336156 PMCID: PMC4919084 DOI: 10.1371/journal.ppat.1005686] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/18/2016] [Indexed: 12/21/2022] Open
Abstract
Plant root border cells have been recently recognized as an important physical defense against soil-borne pathogens. Root border cells produce an extracellular matrix of protein, polysaccharide and DNA that functions like animal neutrophil extracellular traps to immobilize pathogens. Exposing pea root border cells to the root-infecting bacterial wilt pathogen Ralstonia solanacearum triggered release of DNA-containing extracellular traps in a flagellin-dependent manner. These traps rapidly immobilized the pathogen and killed some cells, but most of the entangled bacteria eventually escaped. The R. solanacearum genome encodes two putative extracellular DNases (exDNases) that are expressed during pathogenesis, suggesting that these exDNases contribute to bacterial virulence by enabling the bacterium to degrade and escape root border cell traps. We tested this hypothesis with R. solanacearum deletion mutants lacking one or both of these nucleases, named NucA and NucB. Functional studies with purified proteins revealed that NucA and NucB are non-specific endonucleases and that NucA is membrane-associated and cation-dependent. Single ΔnucA and ΔnucB mutants and the ΔnucA/B double mutant all had reduced virulence on wilt-susceptible tomato plants in a naturalistic soil-soak inoculation assay. The ΔnucA/B mutant was out-competed by the wild-type strain in planta and was less able to stunt root growth or colonize plant stems. Further, the double nuclease mutant could not escape from root border cells in vitro and was defective in attachment to pea roots. Taken together, these results demonstrate that extracellular DNases are novel virulence factors that help R. solanacearum successfully overcome plant defenses to infect plant roots and cause bacterial wilt disease.
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Affiliation(s)
- Tuan Minh Tran
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - April MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Martha Hawes
- Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, United States of America
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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Tran TM, MacIntyre A, Hawes M, Allen C. Escaping Underground Nets: Extracellular DNases Degrade Plant Extracellular Traps and Contribute to Virulence of the Plant Pathogenic Bacterium Ralstonia solanacearum. PLoS Pathog 2016; 12:e1005686. [PMID: 27336156 DOI: 10.1371/journal.ppat.10056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/18/2016] [Indexed: 05/22/2023] Open
Abstract
Plant root border cells have been recently recognized as an important physical defense against soil-borne pathogens. Root border cells produce an extracellular matrix of protein, polysaccharide and DNA that functions like animal neutrophil extracellular traps to immobilize pathogens. Exposing pea root border cells to the root-infecting bacterial wilt pathogen Ralstonia solanacearum triggered release of DNA-containing extracellular traps in a flagellin-dependent manner. These traps rapidly immobilized the pathogen and killed some cells, but most of the entangled bacteria eventually escaped. The R. solanacearum genome encodes two putative extracellular DNases (exDNases) that are expressed during pathogenesis, suggesting that these exDNases contribute to bacterial virulence by enabling the bacterium to degrade and escape root border cell traps. We tested this hypothesis with R. solanacearum deletion mutants lacking one or both of these nucleases, named NucA and NucB. Functional studies with purified proteins revealed that NucA and NucB are non-specific endonucleases and that NucA is membrane-associated and cation-dependent. Single ΔnucA and ΔnucB mutants and the ΔnucA/B double mutant all had reduced virulence on wilt-susceptible tomato plants in a naturalistic soil-soak inoculation assay. The ΔnucA/B mutant was out-competed by the wild-type strain in planta and was less able to stunt root growth or colonize plant stems. Further, the double nuclease mutant could not escape from root border cells in vitro and was defective in attachment to pea roots. Taken together, these results demonstrate that extracellular DNases are novel virulence factors that help R. solanacearum successfully overcome plant defenses to infect plant roots and cause bacterial wilt disease.
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Affiliation(s)
- Tuan Minh Tran
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - April MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Martha Hawes
- Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, United States of America
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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Schulz F, Horn M. Intranuclear bacteria: inside the cellular control center of eukaryotes. Trends Cell Biol 2015; 25:339-46. [PMID: 25680230 DOI: 10.1016/j.tcb.2015.01.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/14/2015] [Accepted: 01/15/2015] [Indexed: 12/17/2022]
Abstract
Intracellular bacteria including major pathogens live in the cytoplasm or in cytoplasmic vacuoles within their host cell. However, some can invade more unusual intracellular niches such as the eukaryotic nucleus. Phylogenetically diverse intranuclear bacteria have been discovered in various protist, arthropod, marine invertebrate, and mammalian hosts. Although targeting the same cellular compartment, they have apparently developed fundamentally-different infection strategies. The nucleus provides a rich pool of nutrients and protection against host cytoplasmic defense mechanisms; intranuclear bacteria can directly manipulate the host by interfering with nuclear processes. The impact on their host cells ranges from stable associations with a neutral or beneficial effect on host fitness to rapid host lysis. The analysis of the intranuclear lifestyle will extend our current framework for understanding host-pathogen interactions.
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Affiliation(s)
- Frederik Schulz
- Department of Microbiology and Ecosystem Science, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Matthias Horn
- Department of Microbiology and Ecosystem Science, University of Vienna, Althanstraße 14, 1090 Vienna, Austria.
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Ceuppens S, Li D, Uyttendaele M, Renault P, Ross P, Ranst MV, Cocolin L, Donaghy J. Molecular Methods in Food Safety Microbiology: Interpretation and Implications of Nucleic Acid Detection. Compr Rev Food Sci Food Saf 2014; 13:551-577. [DOI: 10.1111/1541-4337.12072] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 03/09/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Siele Ceuppens
- Faculty of Bioscience Engineering; Laboratory of Food Microbiology and Food Preservation (LFMFP); Dept. of Food Safety and Food Quality; Ghent Univ.; Ghent Belgium
| | - Dan Li
- Faculty of Bioscience Engineering; Laboratory of Food Microbiology and Food Preservation (LFMFP); Dept. of Food Safety and Food Quality; Ghent Univ.; Ghent Belgium
| | - Mieke Uyttendaele
- Faculty of Bioscience Engineering; Laboratory of Food Microbiology and Food Preservation (LFMFP); Dept. of Food Safety and Food Quality; Ghent Univ.; Ghent Belgium
| | - Pierre Renault
- Inst. Scientifique de Recherche Agronomique (INRA); France
| | - Paul Ross
- Moorepark Biotechnology Centre; Teagasc; Moorepark; Fermoy Co. Cork Ireland
| | | | - Luca Cocolin
- Dept. of Agricultural; Forest and Food Sciences; Univ. of Torino; Grugliasco Torino Italy
| | - John Donaghy
- Food Safety Microbiology Group; Nestle Research Center; Lausanne Switzerland
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9
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Sun Y, Bernardy EE, Hammer BK, Miyashiro T. Competence and natural transformation in vibrios. Mol Microbiol 2013; 89:583-95. [PMID: 23803158 DOI: 10.1111/mmi.12307] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2013] [Indexed: 01/01/2023]
Abstract
Natural transformation is a major mechanism of horizontal gene transfer in bacteria. By incorporating exogenous DNA elements into chromosomes, bacteria are able to acquire new traits that can enhance their fitness in different environments. Within the past decade, numerous studies have revealed that natural transformation is prevalent among members of the Vibrionaceae, including the pathogen Vibrio cholerae. Four environmental factors: (i) nutrient limitation, (ii) availability of extracellular nucleosides, (iii) high cell density and (iv) the presence of chitin, promote genetic competence and natural transformation in Vibrio cholerae by co-ordinating expression of the regulators CRP, CytR, HapR and TfoX respectively. Studies of other Vibrionaceae members highlight the general importance of natural transformation within this bacterial family.
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Affiliation(s)
- Yan Sun
- Department of Biochemistry and Molecular Biology Eberly College of Science The Pennsylvania State University 219 Wartik Lab University Park, PA 16802, USA
| | - Eryn E Bernardy
- School of Biology Georgia Institute of Technology 310 Ferst Drive, Atlanta, GA 30332-0230
| | - Brian K Hammer
- School of Biology Georgia Institute of Technology 310 Ferst Drive, Atlanta, GA 30332-0230
| | - Tim Miyashiro
- Department of Biochemistry and Molecular Biology Eberly College of Science The Pennsylvania State University 219 Wartik Lab University Park, PA 16802, USA
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van Wolferen M, Ajon M, Driessen AJM, Albers SV. How hyperthermophiles adapt to change their lives: DNA exchange in extreme conditions. Extremophiles 2013; 17:545-63. [PMID: 23712907 DOI: 10.1007/s00792-013-0552-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 05/12/2013] [Indexed: 01/24/2023]
Abstract
Transfer of DNA has been shown to be involved in genome evolution. In particular with respect to the adaptation of bacterial species to high temperatures, DNA transfer between the domains of bacteria and archaea seems to have played a major role. In addition, DNA exchange between similar species likely plays a role in repair of DNA via homologous recombination, a process that is crucial under DNA damaging conditions such as high temperatures. Several mechanisms for the transfer of DNA have been described in prokaryotes, emphasizing its general importance. However, until recently, not much was known about this process in prokaryotes growing in highly thermophilic environments. This review describes the different mechanisms of DNA transfer in hyperthermophiles, and how this may contribute to the survival and adaptation of hyperthermophilic archaea and bacteria to extreme environments.
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Affiliation(s)
- Marleen van Wolferen
- Molecular Biology of Archaea, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, 35043 Marburg, Germany
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Petrun B, Lostroh CP. Vibrio fischeriexhibit the growth advantage in stationary-phase phenotype. Can J Microbiol 2013; 59:130-5. [DOI: 10.1139/cjm-2012-0439] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vibrio fischeri are bioluminescent marine bacteria that can be isolated from their symbiotic animal partners or from ocean water. A V. fischeri population increases exponentially inside the light organ of the Hawaiian bobtail squid (Euprymna scolopes) while the host is quiescent during the day. This bacterial light organ population reaches stationary phase and then remains high during the night, when the squid use bacterial bioluminescence as a counter-predation strategy. At dawn, host squid release 90%–95% of the light organ contents into the ocean water prior to burying in the sand for the day. As the squid sleeps, the cycle of bacterial population growth in the light organ begins again. These V. fischeri cells that are vented into the ocean must persist under typical marine low nutrient conditions until they encounter another opportunity to colonize a host. We hypothesized that because V. fischeri regularly encounter cycles of feast and famine in nature, they would exhibit the growth advantage in stationary phase (GASP) phenotype. We found that older V. fischeri cells exhibit a Class 2 GASP response in which old cells increase dramatically in frequency while the population of young V. fischeri cells remains almost constant during co-incubation.
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Affiliation(s)
- Branden Petrun
- Department of Biology, Colorado College, Colorado Springs, CO 80903, USA
| | - C. Phoebe Lostroh
- Department of Biology, Colorado College, Colorado Springs, CO 80903, USA
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Kohl JV. Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. SOCIOAFFECTIVE NEUROSCIENCE & PSYCHOLOGY 2012; 2:17338. [PMID: 24693349 PMCID: PMC3960071 DOI: 10.3402/snp.v2i0.17338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
BACKGROUND Olfactory cues directly link the environment to gene expression. Two types of olfactory cues, food odors and social odors, alter genetically predisposed hormone-mediated activity in the mammalian brain. METHODS The honeybee is a model organism for understanding the epigenetic link from food odors and social odors to neural networks of the mammalian brain, which ultimately determine human behavior. RESULTS Pertinent aspects that extend the honeybee model to human behavior include bottom-up followed by top-down gene, cell, tissue, organ, organ-system, and organism reciprocity; neurophysiological effects of food odors and of sexually dimorphic, species-specific social odors; a model of motor function required for social selection that precedes sexual selection; and hormonal effects that link current neuroscience to social science affects on the development of animal behavior. CONCLUSION As the psychological influence of food odors and social orders is examined in detail, the socioaffective nature of olfactory cues on the biologically based development of sexual preferences across all species that sexually reproduce becomes clearer.
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Affiliation(s)
- James V. Kohl
- James V. Kohl, Independent Researcher, 175 Crimson Lane, Epworth, GA 30541, USA. Tel: (706) 455-7967.
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Yuan M, Zhu Y, Lou X, Chen C, Wei G, Lan M, Zhao J. Sensitive label-free oligonucleotide-based microfluidic detection of mercury (II) ion by using exonuclease I. Biosens Bioelectron 2012; 31:330-6. [DOI: 10.1016/j.bios.2011.10.043] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 10/10/2011] [Accepted: 10/19/2011] [Indexed: 02/06/2023]
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Abstract
Uptake signal sequences are DNA motifs that promote DNA uptake by competent bacteria in the family Pasteurellaceae and the genus Neisseria. The genomes of these bacteria contain many copies of their canonical uptake sequence (often >100-fold overrepresentation), so the bias of the uptake machinery causes cells to prefer DNA derived from close relatives over DNA from other sources. However, the molecular and evolutionary forces responsible for the abundance of uptake sequences in these genomes are not well understood, and their presence is not easily explained by any of the current models of the evolution of competence. Here we describe use of a computer simulation model to thoroughly evaluate the simplest explanation for uptake sequences, that they accumulate in genomes by a form of molecular drive generated by biased DNA uptake and evolutionarily neutral (i.e., unselected) recombination. In parallel we used an unbiased search algorithm to characterize genomic uptake sequences and DNA uptake assays to refine the Haemophilus influenzae uptake specificity. These analyses showed that biased uptake and neutral recombination are sufficient to drive uptake sequences to high densities, with the spacings, stabilities, and strong consensus typical of uptake sequences in real genomes. This result greatly simplifies testing of hypotheses about the benefits of DNA uptake, because it explains how genomes could have passively accumulated sequences matching the bias of their uptake machineries.
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