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Gonzalez D, Mavridou DA. Making the Best of Aggression: The Many Dimensions of Bacterial Toxin Regulation. Trends Microbiol 2019; 27:897-905. [DOI: 10.1016/j.tim.2019.05.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 05/15/2019] [Accepted: 05/23/2019] [Indexed: 12/14/2022]
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2
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Wojciech J, Kamila M, Wojciech B. Investigation of the population dynamics within a Pseudomonas aeruginosa biofilm using a flow based biofilm model system and flow cytometric evaluation of cellular physiology. BIOFOULING 2018; 34:835-850. [PMID: 30332894 DOI: 10.1080/08927014.2018.1508569] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Revised: 07/16/2018] [Accepted: 07/25/2018] [Indexed: 06/08/2023]
Abstract
In this study a flow based biofilm model system was used to simulate the formation of Pseudomonas aeruginosa biofilms on a stainless steel surface. To investigate the complexity of biofilm-associated P. aeruginosa populations a combination of microscopic observations and flow cytometric analysis (FCM) was adopted. Biofilm-associated P. aeruginosa cells were evaluated (1) under optimal vs reduced nutrient-availability at the initial adhesion stage, and (2) irrespective of nutrient-availability within a mature biofilm. Microscopic estimation of the extent of attachment revealed more effective colonization upon optimal vs starvation conditions. FCM allowed an in situ evaluation of P. aeruginosa vitality, using cellular redox potential measurements to discriminate active, mid-active and non-active sub-populations. Samples from recently attached cells and mature biofilms showed significant differences in the percentages of bacterial cells from the defined sub-populations. The approach demonstrated that distribution of individual P. aeruginosa sub-populations was influenced by the stage of the biofilm life-cycle and nutrient availability.
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Affiliation(s)
- Juzwa Wojciech
- a Department of Biotechnology and Food Microbiology , Poznan University of Life Sciences , Poznan , Poland
| | - Myszka Kamila
- a Department of Biotechnology and Food Microbiology , Poznan University of Life Sciences , Poznan , Poland
| | - Białas Wojciech
- a Department of Biotechnology and Food Microbiology , Poznan University of Life Sciences , Poznan , Poland
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Mavridou DAI, Gonzalez D, Kim W, West SA, Foster KR. Bacteria Use Collective Behavior to Generate Diverse Combat Strategies. Curr Biol 2018; 28:345-355.e4. [PMID: 29395918 DOI: 10.1016/j.cub.2017.12.030] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 11/06/2017] [Accepted: 12/14/2017] [Indexed: 01/06/2023]
Abstract
Animals have evolved a wide diversity of aggressive behavior often based upon the careful monitoring of other individuals. Bacteria are also capable of aggression, with many species using toxins to kill or inhibit their competitors. Like animals, bacteria also have systems to monitor others during antagonistic encounters, but how this translates into behavior remains poorly understood. Here, we use colonies of Escherichia coli carrying colicin-encoding plasmids as a model for studying antagonistic behavior. We show that in the absence of threat, dispersed cells with low reproductive value produce colicin toxins spontaneously, generating efficient pre-emptive attacks. Cells can also respond conditionally to toxins released by clonemates via autoinduction or other genotypes via competition sensing. The strength of both pre-emptive and responsive attacks varies widely between strains. We demonstrate that this variability occurs easily through mutation by rationally engineering strains to recapitulate the diversity in naturally occurring strategies. Finally, we discover that strains that can detect both competitors and clonemates are capable of massive coordinated attacks on competing colonies. This collective behavior protects established colonies from competitors, mirroring the evolution of alarm calling in the animal world.
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Affiliation(s)
- Despoina A I Mavridou
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK; MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, Kensington, London SW7 2DD, UK
| | - Diego Gonzalez
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK
| | - Wook Kim
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
| | - Stuart A West
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK
| | - Kevin R Foster
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK.
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4
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Coray DS, Kurenbach B, Heinemann JA. Exploring the parameters of post-segregational killing using heterologous expression of secreted toxin barnase and antitoxin barstar in an Escherichia coli case study. MICROBIOLOGY-SGM 2017; 163:122-130. [PMID: 28270261 DOI: 10.1099/mic.0.000395] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Post-segregational killing (PSK) is a phenotype determined by plasmids using a toxin and an antitoxin gene pair. Loss of the genes depletes the cell's reserve of antitoxin and allows the toxin to act upon the cell. PSK benefits mobile elements when it increases reproductive success relative to other mobile competitors. A side effect of PSK is that plasmids become refractory to displacement from the cell during growth as a monoculture. Most PSK systems use a cytoplasmic toxin, but the external toxins of bacteriocins also have a PSK-like effect. It may be that any toxin and antitoxin gene pair can demonstrate PSK when it is on a plasmid. The secreted ribonuclease barnase and its protein inhibitor barstar have features in common with PSK modules, though their native context is chromosomal. We hypothesized that their recruitment to a plasmid could produce an emergent PSK phenotype. Others had shown that secreted barnase could exert a lethal effect on susceptible bacteria similarly to bacteriocins. However, barnase toxicity did not occur under the conditions tested, suggesting that barnase is toxic to neighbouring cells only under very specific conditions. Bacteriocins are only produced under some conditions, and some conditionality on toxin function or release may be advantageous in general to PSKs with external toxins because it would prevent killing of potential plasmid-naive hosts. Too much conditionality, however, would limit how advantageous the gene pair was to mobile elements, making the genes unlikely to be recruited as a PSK system.
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Affiliation(s)
- Dorien S Coray
- Centre for Integrative Ecology and Centre for Integrated Research in Biosafety, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.,School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
| | - Brigitta Kurenbach
- Centre for Integrative Ecology and Centre for Integrated Research in Biosafety, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.,School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
| | - Jack A Heinemann
- Centre for Integrative Ecology and Centre for Integrated Research in Biosafety, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.,School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
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5
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Ghazaryan L, Tonoyan L, Ashhab AA, Soares MIM, Gillor O. The role of stress in colicin regulation. Arch Microbiol 2014; 196:753-64. [PMID: 25048159 DOI: 10.1007/s00203-014-1017-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 07/05/2014] [Accepted: 07/11/2014] [Indexed: 12/28/2022]
Abstract
Bacteriocins produced by Enterobacteriaceae are high molecular weight toxic proteins that kill target cells through a variety of mechanisms, including pore formation and nucleic acid degradation. What is remarkable about these toxins is that their expression results in death to the producing cells and therefore bacteriocin induction have to be tightly regulated, often confined to times of stress. Information on the regulation of bacteriocins produced by enteric bacteria is sketchy as their expression has only been elucidated in a handful of bacteria. Here, we review the known regulatory mechanisms of enteric bacteriocins and explore the expression of 12 of them in response to various triggers: DNA-damaging agents, stringent response, catabolite repression, oxidative stress, growth phase, osmolarity, cold shock, nutrient deprivation, anaerobiosis and pH stress. Our results indicate that the expression of bacteriocins is mostly confined to mutagenic triggers, while all other triggers tested are limited inducers.
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Affiliation(s)
- Lusine Ghazaryan
- Zuckerberg Institute for Water Research, J. Blaustein Institutes for Desert Research, Ben-Gurion University, 84990, Midreshet Ben-Gurion, Israel
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Crnigoj M, Podlesek Z, Budič M, Zgur-Bertok D. The Escherichia coli uropathogenic-specific-protein-associated immunity protein 3 (Imu3) has nucleic acid -binding activity. BMC Microbiol 2014; 14:16. [PMID: 24472116 PMCID: PMC3917654 DOI: 10.1186/1471-2180-14-16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 01/20/2014] [Indexed: 11/19/2022] Open
Abstract
Background The Escherichia coli uropathogenic-specific protein (Usp) is a bacteriocin-like genotoxin, active against mammalian cells and associated with E. coli strains that provoke pyelonephritis, prostatitis and bacteraemia. Usp is encoded by a small pathogenicity island with three downstream small open reading frames (Imu1-3) that are believed to provide immunity to the producer. To prevent host suicide, colicins, bacteriocins of E. coli, form tight complexes with their cognate immunity proteins. Colicin – immunity protein complexes are among the strongest protein complexes known. Here, the Usp associated immunity protein 3 (Imu3) was partially characterized to gain insight into its role and mechanism of activity. Results Isolation and partial characterisation of the Usp-associated immunity protein-3 (Imu3) revealed that, while Usp and Imu3 do not form a high affinity complex, Imu3 exhibits DNA and RNA binding activity. Imu3 was also shown to protect DNA against degradation by colicin E7. Conclusions Our data infer that nonspecific DNA binding of the Imu3 immunity protein, prevents suicide of E. coli producing the genotoxin Usp.
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Affiliation(s)
| | | | | | - Darja Zgur-Bertok
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
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Bano S, Vankemmelbeke M, Penfold CN, James R. Pattern of induction of colicin E9 synthesis by sub MIC of Norfloxacin antibiotic. Microbiol Res 2013; 168:661-6. [DOI: 10.1016/j.micres.2013.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 04/01/2013] [Accepted: 04/04/2013] [Indexed: 11/28/2022]
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Regulating colicin synthesis to cope with stress and lethality of colicin production. Biochem Soc Trans 2013; 40:1507-11. [PMID: 23176507 DOI: 10.1042/bst20120184] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Colicins are plasmid-encoded bacteriocins active against Escherichia coli and closely related species of Enterobacteriaceae. They promote microbial diversity and genetic diversity in E. coli populations. Colicin synthesis is characteristically repressed by the LexA protein, the key regulator of the SOS response. As colicins are released by cell lysis, generally two LexA dimers binding to two overlapping SOS boxes control untimely expression. Nevertheless, genetic organization of the colicin clusters, additional transcription regulators as well as post-transcriptional mechanisms involving translational efficiency of the lysis and activity genes fine-tune colicin expression and protect against lethality of colicin production.
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Najafabadi HS, Goodarzi H, Salavati R. Universal function-specificity of codon usage. Nucleic Acids Res 2010; 37:7014-23. [PMID: 19773421 PMCID: PMC2790905 DOI: 10.1093/nar/gkp792] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Synonymous codon usage has long been known as a factor that affects average expression level of proteins in fast-growing microorganisms, but neither its role in dynamic changes of expression in response to environmental changes nor selective factors shaping it in the genomes of higher eukaryotes have been fully understood. Here, we propose that codon usage is ubiquitously selected to synchronize the translation efficiency with the dynamic alteration of protein expression in response to environmental and physiological changes. Our analysis reveals that codon usage is universally correlated with gene function, suggesting its potential contribution to synchronized regulation of genes with similar functions. We directly show that coexpressed genes have similar synonymous codon usages within the genomes of human, yeast, Caenorhabditis elegans and Escherichia coli. We also demonstrate that perturbing the codon usage directly affects the level or even direction of changes in protein expression in response to environmental stimuli. Perturbing tRNA composition also has tangible phenotypic effects on the cell. By showing that codon usage is universally function-specific, our results expand, to almost all organisms, the notion that cells may need to dynamically alter their intracellular tRNA composition in order to adapt to their new environment or physiological role.
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Affiliation(s)
- Hamed Shateri Najafabadi
- Institute of Parasitology, McGill University, 21111 Lakeshore Road, Ste. Anne de Bellevue, Montreal, Quebec, H9X3V9, Canada
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Kloster M, Tang C. SCUMBLE: a method for systematic and accurate detection of codon usage bias by maximum likelihood estimation. Nucleic Acids Res 2008; 36:3819-27. [PMID: 18495752 PMCID: PMC2441815 DOI: 10.1093/nar/gkn288] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 04/22/2008] [Accepted: 04/25/2008] [Indexed: 11/23/2022] Open
Abstract
The genetic code is degenerate--most amino acids can be encoded by from two to as many as six different codons. The synonymous codons are not used with equal frequency: not only are some codons favored over others, but also their usage can vary significantly from species to species and between different genes in the same organism. Known causes of codon bias include differences in mutation rates as well as selection pressure related to the expression level of a gene, but the standard analysis methods can account for only a fraction of the observed codon usage variation. We here introduce an explicit model of codon usage bias, inspired by statistical physics. Combining this model with a maximum likelihood approach, we are able to clearly identify different sources of bias in various genomes. We have applied the algorithm to Saccharomyces cerevisiae as well as 325 prokaryote genomes, and in most cases our model explains essentially all observed variance.
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Affiliation(s)
- Morten Kloster
- Department of Bioengineering and Therapeutic Sciences, UCSF, San Francisco, California 94158, USA and Center for Theoretical Biology, Peking University, Beijing 100871, China
| | - Chao Tang
- Department of Bioengineering and Therapeutic Sciences, UCSF, San Francisco, California 94158, USA and Center for Theoretical Biology, Peking University, Beijing 100871, China
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11
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Abstract
As Escherichia coli strains enter the stationary phase of growth they become more resistant to the peptide antibiotic microcin J25. It is known that starvation for nutrients such as amino acids or glucose leads to increases in guanosine 3',5'-bispyrophosphate (ppGpp) levels and that the intracellular concentration of this nucleotide increases as cells enter the stationary phase of growth. Therefore, we examined the effects of artificially manipulating the ppGpp levels on sensitivity to microcin J25. A direct correlation was found between ppGpp accumulation and microcin resistance. Our results indicate that the nucleotide is required to induce production of YojI, a chromosomally encoded efflux pump which, in turn, expels microcin from cells. This would maintain the intracellular level of the antibiotic below a toxic level.
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12
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Butala M, Podlesek Z, Zgur-Bertok D. The SOS response affects thermoregulation of colicin K synthesis. FEMS Microbiol Lett 2008; 283:104-11. [PMID: 18399998 DOI: 10.1111/j.1574-6968.2008.01161.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Temperature is one of the key environmental parameters affecting bacterial gene expression. This study investigated the effect of temperature on synthesis of Escherichia coli colicins E1, K, N and E7 as well as the molecular basis underlying thermoregulation of the colicin K activity gene cka. The results of our study show that synthesis of the investigated colicins is higher at 37 degrees C than at 22 degrees C and that temperature regulates cka expression at the level of transcription. We propose that the SOS response indirectly regulates thermoregulation of colicin K (and possibly of the other examined colicins). Two LexA dimers bind cooperatively with high affinity to the two overlapping LexA boxes in a temperature-independent manner. At 22 degrees C the relative degree of repression is higher as a result of less LexA cleavage due to a slower growth rate, while at 37 degrees C the extent of LexA cleavage is higher due to a higher growth rate. Thermoregulation of colicin synthesis is an additional example of the connection between the SOS regulon and cell physiology.
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Affiliation(s)
- Matej Butala
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
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13
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Abstract
The production of (p)ppGpp by Streptococcus mutans UA159 is catalyzed by three gene products: RelA, RelP, and RelQ. Here, we investigate the role of the RelA (Rel) homologue of S. mutans in the stringent response and in the global control of gene expression. RelA of S. mutans was shown to synthesize pppGpp in vitro from GTP and ATP in the absence of added ribosomes, as well as in vivo in an Escherichia coli relA-spoT mutant. Mupirocin (MUP) was shown to induce high levels of (p)ppGpp production in S. mutans in a relA-dependent manner, with a concomitant reduction in GTP pools. Transcription profiling after MUP treatment of S. mutans revealed that 104 genes were upregulated and 130 were downregulated (P < or = 0.001); mainly, genes for macromolecular biosynthesis, translation, and energy metabolism were downregulated. When a derivative of UA159 carrying a complete deletion of the relA gene was treated with MUP, 72 genes were upregulated and 52 were downregulated (P < or = 0.001). The expression of 50 genes (P < or = 0.001) was commonly affected by MUP treatment in the two strains, suggesting that S. mutans can mount a relA-independent response to MUP. Consistent with the gene expression profiling, RelA was shown to play major roles in the regulation of phenotypic traits that are required for establishment, persistence, and virulence expression by this oral pathogen. Thus, RelA is the major (p)ppGpp synthase controlling the stringent response in S. mutans, and it coordinates the expression of genes and phenotypes that contribute to the pathogenic potential of the organism.
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Sajish M, Tiwari D, Rananaware D, Nandicoori VK, Prakash B. A charge reversal differentiates (p)ppGpp synthesis by monofunctional and bifunctional Rel proteins. J Biol Chem 2007; 282:34977-83. [PMID: 17911108 DOI: 10.1074/jbc.m704828200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A major regulatory mechanism evolved by microorganisms to combat stress is the regulation mediated by (p)ppGpp (the stringent response molecule), synthesized and hydrolyzed by Rel proteins. These are divided into bifunctional and monofunctional proteins based on the presence or absence of the hydrolysis activity. Although these proteins require Mg(2+) for (p)ppGpp synthesis, high Mg(2+) was shown to inhibit this reaction in bifunctional Rel proteins from Mycobacterium tuberculosis and Streptococcus equisimilis. This is not a characteristic feature in enzymes that use a dual metal ion mechanism, such as DNA polymerases that are known to carry out a similar pyrophosphate transfer reaction. Comparison of polymerase Polbeta and Rel(Seq) structures that share a common fold led to the proposal that the latter would follow a single metal ion mechanism. Surprisingly, in contrast to bifunctional Rel, we did not find inhibition of guanosine 5'-triphosphate, 3'-diphosphate (pppGpp) synthesis at higher Mg(2+) in the monofunctional RelA from Escherichia coli. We show that a charge reversal in a conserved motif in the synthesis domains explains this contrast; an RXKD motif in the bifunctional proteins is reversed to an EXDD motif. The differential response of these proteins to Mg(2+) could also be noticed in fluorescent nucleotide binding and circular dichroism experiments. In mutants where the motifs were reversed, the differential effect could also be reversed. We infer that although a catalytic Mg(2+) is common to both bifunctional and monofunctional proteins, the latter would utilize an additional metal binding site formed by EXDD. This work, for the first time, brings out differences in (p)ppGpp synthesis by the two classes of Rel proteins.
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Affiliation(s)
- Mathew Sajish
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, 208016 India
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15
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Cascales E, Buchanan SK, Duché D, Kleanthous C, Lloubès R, Postle K, Riley M, Slatin S, Cavard D. Colicin biology. Microbiol Mol Biol Rev 2007; 71:158-229. [PMID: 17347522 PMCID: PMC1847374 DOI: 10.1128/mmbr.00036-06] [Citation(s) in RCA: 784] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.
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Affiliation(s)
- Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires,Institut de Biologie Structurale et Microbiologie, Centre National de la Recherche Scientifique, UPR 9027, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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16
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Mrak P, Podlesek Z, van Putten JPM, Zgur-Bertok D. Heterogeneity in expression of the Escherichia coli colicin K activity gene cka is controlled by the SOS system and stochastic factors. Mol Genet Genomics 2007; 277:391-401. [PMID: 17216493 DOI: 10.1007/s00438-006-0185-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Accepted: 10/17/2006] [Indexed: 10/23/2022]
Abstract
Phenotypic diversity provides populations of prokaryotic and eukaryotic organisms with the flexibility required to adapt to and/or survive environmental perturbations. Consequently, there is much interest in unraveling the molecular mechanisms of heterogeneity. A classical example of heterogeneity in Escherichia coli is the subset (3%) of the population that expresses the colicin K activity gene (cka) upon nutrient starvation. Here, we report on the mechanism underlying this variable response. As colicin synthesis is regulated by the LexA protein, the central regulator of the SOS response, we focused on the role of LexA and the SOS system in the variable cka expression. Real-time RT-PCR showed that the SOS system, without exogenous DNA damage, induces moderate levels of cka expression. The use of cka-gfp fusions demonstrated that modification of the conserved LexA boxes in the cka promoter region affected LexA binding affinity and the percentage of cka-gfp expressing cells in the population. A lexA-gfp fusion showed that the lexA gene is highly expressed in a subset of bacteria. Furthermore, cka-gfp fusions cloned into higher copy plasmid vectors increased the percentage of cka-gfp positive bacteria. Together, these results indicate that the bistability in cka expression in the bacterial population is determined by (1) basal SOS activity, (2) stochastic factors and possibly (3) the interplay of LexA dimers at cka operator. Other LexA regulated processes could exhibit similar regulation.
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Affiliation(s)
- Peter Mrak
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000, Ljubljana, Slovenia
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17
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Rijavec M, Budic M, Mrak P, Müller-Premru M, Podlesek Z, Zgur-Bertok D. Prevalence of ColE1-like plasmids and colicin K production among uropathogenic Escherichia coli strains and quantification of inhibitory activity of colicin K. Appl Environ Microbiol 2006; 73:1029-32. [PMID: 17122402 PMCID: PMC1800769 DOI: 10.1128/aem.01780-06] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Colicin K exhibited pronounced inhibitory activity against uropathogenic Escherichia coli (UPEC) strains. Low prevalence of colicin K production and a relatively high prevalence of ColE1-like plasmids were determined among 215 UPEC strains from Slovenia. Sequencing of the colicin K-encoding pColK-K235 revealed a mosaic structure and the presence of the insertion sequence IS2.
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Affiliation(s)
- Matija Rijavec
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, Ljubljana, Slovenia
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18
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Smits WK, Kuipers OP, Veening JW. Phenotypic variation in bacteria: the role of feedback regulation. Nat Rev Microbiol 2006; 4:259-71. [PMID: 16541134 DOI: 10.1038/nrmicro1381] [Citation(s) in RCA: 397] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To survive in rapidly changing environmental conditions, bacteria have evolved a diverse set of regulatory pathways that govern various adaptive responses. Recent research has reinforced the notion that bacteria use feedback-based circuitry to generate population heterogeneity in natural situations. Using artificial gene networks, it has been shown that a relatively simple 'wiring' of a bacterial genetic system can generate two or more stable subpopulations within an overall genetically homogeneous population. This review discusses the ubiquity of these processes throughout nature, as well as the presumed molecular mechanisms responsible for the heterogeneity observed in a selection of bacterial species.
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Affiliation(s)
- Wiep Klaas Smits
- Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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Shu P, Dai H, Gao W, Goldman E. Inhibition of translation by consecutive rare leucine codons in E. coli: absence of effect of varying mRNA stability. Gene Expr 2006; 13:97-106. [PMID: 17017124 PMCID: PMC6032470 DOI: 10.3727/000000006783991881] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Consecutive homologous codons that are rarely used in E. coli are known to inhibit translation to varying degrees. As few as two consecutive rare arginine codons exhibit a profound inhibition of translation when they are located in the 5' portion of a gene in E. coli. We have previously shown that nine consecutive rare CUA leucine codons cause almost complete inhibition of translation when they are placed after the 13th codon of a test message (although they do not inhibit translation when they are placed in the middle of the message). In the present work, we report that five consecutive rare CUA leucine codons exhibit approximately a threefold inhibition of translation when they are similarly placed after the 13th codon of a test message, compared to five consecutive common CUG leucine codons, in a T7 RNA polymerase-driven system. Further, by removing RNase III processing sites at the 3' ends of the mRNAs, we have manipulated the stability of the mRNAs encoding the test and control messages to see if decreasing mRNA stability might have an effect on the extent of translation inhibition by the rare leucine codons. However, the inhibition with the less stable mRNAs was similar to that with the stable mRNAs, approximately 3.4-fold, indicating that mRNA stability per se does not have a major influence on the effects of rare codons in this system.
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Affiliation(s)
- Ping Shu
- Department of Microbiology & Molecular Genetics, New Jersey Medical School, University of Medicine & Dentistry of New Jersey, Newark, NJ 07101-1709, USA
| | - Huacheng Dai
- Department of Microbiology & Molecular Genetics, New Jersey Medical School, University of Medicine & Dentistry of New Jersey, Newark, NJ 07101-1709, USA
| | - Wenwu Gao
- Department of Microbiology & Molecular Genetics, New Jersey Medical School, University of Medicine & Dentistry of New Jersey, Newark, NJ 07101-1709, USA
| | - Emanuel Goldman
- Department of Microbiology & Molecular Genetics, New Jersey Medical School, University of Medicine & Dentistry of New Jersey, Newark, NJ 07101-1709, USA
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20
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Budin-Verneuil A, Pichereau V, Auffray Y, Ehrlich DS, Maguin E. Proteomic characterization of the acid tolerance response inLactococcus lactis MG1363. Proteomics 2005; 5:4794-807. [PMID: 16237734 DOI: 10.1002/pmic.200401327] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Exponentially growing cells of Lactococcus lactis MG1363 are able to develop an Acid Tolerance Response (ATR) when incubated at pH 5, in both rich (M17)--and chemically defined (SA)--culture media. Physiological and proteomic characterization of this adaptive response indicated that L. lactis reorganizes its metabolism in response to acid stress to a great extent and quite differently in the two media. The development of ATR was fully dependent on protein de novo synthesis in SA and only partly dependent in M17. 2D gel electrophoresis revealed a total of 90 spots induced by acidity, 80 of which were identified by mass spectrometry. Only 10 proteins (BglA, PycA, GlmS, HasC, ArgS, GatA, AtpA, ArcB, Cfa, and SodA) were overproduced in the two media. A transcriptional analysis of the corresponding genes suggested that for half of them the mode of regulation may differ in the two media. Among the protein spots upregulated during the ATR in SA but not in M17, 13 already displayed an elevated rate of synthesis in M17 at neutral pH. These proteins could play an important role in the development of the protein de novo synthesis-independent ATR observed in M17.
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Affiliation(s)
- Aurélie Budin-Verneuil
- Laboratoire Microbiologie de l'Environnement, Université de Caen, F-14032 Caen cedex, France
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21
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Gladitz J, Shen K, Antalis P, Hu FZ, Post JC, Ehrlich GD. Codon usage comparison of novel genes in clinical isolates of Haemophilus influenzae. Nucleic Acids Res 2005; 33:3644-58. [PMID: 15983137 PMCID: PMC1160521 DOI: 10.1093/nar/gki670] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A similarity statistic for codon usage was developed and used to compare novel gene sequences found in clinical isolates of Haemophilus influenzae with a reference set of 80 prokaryotic, eukaryotic and viral genomes. These analyses were performed to obtain an indication as to whether individual genes were Haemophilus-like in nature, or if they probably had more recently entered the H.influenzae gene pool via horizontal gene transfer from other species. The average and SD values were calculated for the similarity statistics from a study of the set of all genes in the H.influenzae Rd reference genome that encoded proteins of 100 amino acids or longer. Approximately 80% of Rd genes gave a statistic indicating that they were most like other Rd genes. Genes displaying codon usage statistics >1 SD above this range were either considered part of the highly expressed group of H.influenzae genes, or were considered of foreign origin. An alternative determinant for identifying genes of foreign origin was when the similarity statistics produced a value that was much closer to a non-H.influenzae reference organism than to any of the Haemophilus species contained in the reference set. Approximately 65% of the novel sequences identified in the H.influenzae clinical isolates displayed codon usages most similar to Haemophilus sp. The remaining novel sequences produced similarity statistics closer to one of the other reference genomes thereby suggesting that these sequences may have entered the H.influenzae gene pool more recently via horizontal transfer.
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Affiliation(s)
| | | | | | | | | | - Garth D. Ehrlich
- To whom correspondence should be addressed. Tel: +1 412 359 4228; Fax: +1 412 359 6995;
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22
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Erickson DL, Lines JL, Pesci EC, Venturi V, Storey DG. Pseudomonas aeruginosa relA contributes to virulence in Drosophila melanogaster. Infect Immun 2004; 72:5638-45. [PMID: 15385461 PMCID: PMC517598 DOI: 10.1128/iai.72.10.5638-5645.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The stringent response is a mechanism by which bacteria adapt to nutritional deficiencies through the production of the guanine nucleotides ppGpp and pppGpp, produced by the RelA enzyme. We investigated the role of the relA gene in the ability of an extracellular pathogen, Pseudomonas aeruginosa, to cause infection. Strains lacking the relA gene were created from the prototypical laboratory strain PAO1 as well as the mucoid cystic fibrosis isolate 6106, which lacks functional quorum-sensing systems. The absence of relA abolished the production of ppGpp and pppGpp under conditions of amino acid starvation. We found that strains lacking relA exhibited reduced virulence in a D. melanogaster feeding assay. In conditions of low magnesium, the relA gene enhanced production of the cell-cell signal N-[3-oxododecanoyl]-l-homoserine lactone, whereas relA reduced the production of the 2-heptyl-3-hydroxy-4-quinolone signal during serine hydroxamate induction of the stringent response. In the relA mutant, alterations in the Pseudomonas quinolone system pathways seemed to increase the production of pyocyanin and decrease the production of elastase. Deletion of relA also resulted in reduced levels of the RpoS sigma factor. These results suggest that adjustment of cellular ppGpp and pppGpp levels could be an important regulatory mechanism in P. aeruginosa adaptation in pathogenic relationships.
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Affiliation(s)
- David L Erickson
- Department of Biological Sciences, University of Calgary, Alberta, Canada
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23
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Jin W, Ryu YG, Kang SG, Kim SK, Saito N, Ochi K, Lee SH, Lee KJ. Two relA/spoT homologous genes are involved in the morphological and physiological differentiation of Streptomyces clavuligerus. MICROBIOLOGY-SGM 2004; 150:1485-1493. [PMID: 15133110 DOI: 10.1099/mic.0.26811-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study is focused on the involvement of the unusual nucleotide (p)ppGpp during the morphological and physiological differentiation of Streptomyces clavuligerus. In particular, the functional and structural elements of two genes encoding the proteins RelA and Rsh were identified. The relA gene encodes an 843 aa protein (RelA), while the rsh gene encodes a 738 aa protein (Rsh). The relA and rsh genes were disrupted by the insertion of a hygromycin resistance gene and an apramycin resistance gene, respectively. The synthesis of ppGpp in the relA gene-disrupted mutant was completely eliminated under conditions of starvation for amino acids, whereas synthesis persisted, but was greatly reduced in the rsh gene-disrupted mutant. The relA gene-disrupted mutant had a bald appearance on agar plate cultures and retarded growth in submerged culture, while the rsh-disrupted mutant was unchanged in growth characteristics relative to the wild-type culture. The production of both clavulanic acid and cephamycin C were completely abolished in the relA-disrupted mutant. Thus, it is concluded that the relA gene rather than rsh is essential for morphological and physiological differentiation in S. clavuligerus and that RelA primarily governs the stringent response of S. clavuligerus to starvation for amino acids.
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Affiliation(s)
- Wook Jin
- School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Yong Gu Ryu
- School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Sung Gyun Kang
- School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Sung Keun Kim
- School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Natsumi Saito
- National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan
| | - Kozo Ochi
- National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan
| | - Sang Hee Lee
- Department of Biological Science, Myongji University, Yongin, Kyunggido 449-728, Korea
| | - Kye Joon Lee
- School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
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24
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Hogg T, Mechold U, Malke H, Cashel M, Hilgenfeld R. Conformational antagonism between opposing active sites in a bifunctional RelA/SpoT homolog modulates (p)ppGpp metabolism during the stringent response [corrected]. Cell 2004; 117:57-68. [PMID: 15066282 DOI: 10.1016/s0092-8674(04)00260-0] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2003] [Revised: 01/13/2004] [Accepted: 01/28/2004] [Indexed: 10/26/2022]
Abstract
Enzymes of the Rel/Spo family enable bacteria to survive prolonged periods of nutrient limitation by producing an intracellular signaling alarmone, (p)ppGpp, which triggers the so-called stringent response. Both the synthesis of (p)ppGpp from ATP and GDP(GTP), and its hydrolysis to GDP(GTP) and pyrophosphate, are catalyzed by Rel/Spo proteins. The 2.1 A crystal structure of the bifunctional catalytic fragment of the Rel/Spo homolog from Streptococcus dysgalactiae subsp. equisimilis, Rel(Seq), reveals two conformations of the enzyme corresponding to known reciprocal activity states: (p)ppGpp-hydrolase-OFF/(p)ppGpp-synthetase-ON and hydrolase-ON/synthetase-OFF. The hydrolase and synthetase domains bear remarkable similarities to the catalytic domains of the cyclic phosphodiesterase and nucleotidyltransferase superfamilies, respectively. The active sites, separated by more than 30 A, contain bound nucleotides including an unusual (p)ppGpp derivative, GDP-2':3'-cyclic monophosphate. Reciprocal regulation of the antagonistic catalytic activities, suggested by the structure, is supported by mutagenesis experiments and appears to involve ligand-induced signal transmission between the two active sites.
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Affiliation(s)
- Tanis Hogg
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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25
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Abstract
In species having a strong correlation of expressivity and codon bias it has been shown that heterologous expression can be optimized by changing codons of the introduced gene towards the set of codons that the host organism naturally uses in its highly expressed genes. Even though two lactic acid bacteria are fully sequenced, there are no reports on attempts of codon optimization in the literature. In this report it is demonstrated that codons used in highly expressed genes tend to differ from the codons in lowly expressed genes, and that there is a strong correlation of codon bias and empirical expressivity (codon adaptation index) in Lactococcus lactis and Lactobacillus plantarum. This strongly suggests that codon optimization strategies could be applied to expression systems with lactic acid bacteria as producer strains. A good example of a candidate for codon optimization is the mouse interleukin-2 gene, which in its natural form has an extremely low codon adaptation index for expression in Lc. lactis.
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Affiliation(s)
- Anders Fuglsang
- Institute of Pharmacology, Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK-2100, Copenhagen Ø, Denmark.
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26
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Mulec J, Podlesek Z, Mrak P, Kopitar A, Ihan A, Zgur-Bertok D. A cka-gfp transcriptional fusion reveals that the colicin K activity gene is induced in only 3 percent of the population. J Bacteriol 2003; 185:654-9. [PMID: 12511512 PMCID: PMC145340 DOI: 10.1128/jb.185.2.654-659.2003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In prokaryotes, only a few examples of differential gene expression in cell populations have been described. Colicin production in natural populations of Escherichia coli, while providing a competitive advantage in the natural habitat, also leads to lysis of the toxin-producing cell. Colicin K synthesis has been found to be induced due to an increase in ppGpp (I. Kuhar, J. P. van Putten, D. Zgur-Bertok, W. Gaastra, and B. J. Jordi, Mol. Microbiol. 41:207-216). Using two transcriptional fusions, cka-gfp and cki-gfp, we show that at the single-cell level, the colicin K activity gene cka is expressed in only 3% of the bacterial population upon induction by nutrient starvation. In contrast, the immunity gene cki is expressed in the large majority of the cells. Expression of the cka-gfp fusion in a lexA-defective strain and in a relA spoT mutant strain indicates that differential expression of cka is established primarily at the level of transcription.
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Affiliation(s)
- Janez Mulec
- Karst Research Institute, Scientific Centre of the Slovenian Academy of Sciences and Arts, Postojna, Slovenia
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27
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Mukamolova GV, Kaprelyants AS, Kell DB, Young M. Adoption of the transiently non-culturable state — a bacterial survival strategy? Adv Microb Physiol 2003; 47:65-129. [PMID: 14560663 DOI: 10.1016/s0065-2911(03)47002-1] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Microbial culturability can be ephemeral. Cells are not merely either dead or alive but can adopt physiological states in which they appear to be (transiently) non-culturable under conditions in which they are known normally to be able to grow and divide. The reacquisition of culturability from such states is referred to as resuscitation. We here develop the idea that this "transient non-culturability" is a consequence of a special survival strategy, and summarise the morphological, physiological and genetic evidence underpinning such behaviour and its adaptive significance.
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Affiliation(s)
- Galina V Mukamolova
- Institute of Biological Sciences, University of Wales, Aberystwyth, Ceredigion SY23 3DD, UK
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28
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Mechold U, Murphy H, Brown L, Cashel M. Intramolecular regulation of the opposing (p)ppGpp catalytic activities of Rel(Seq), the Rel/Spo enzyme from Streptococcus equisimilis. J Bacteriol 2002; 184:2878-88. [PMID: 12003927 PMCID: PMC135074 DOI: 10.1128/jb.184.11.2878-2888.2002] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Catalytic and regulatory domains of the Rel/Spo homolog of Streptococcus equisimilis affecting (p)ppGpp synthesis and degradation activities have been defined, and opposing activities of the purified protein and its fragments have been compared. Two major domains of the 739-residue Rel(Seq) protein are defined by limited proteolytic digestion. In vitro assays of the purified N-terminal half-protein reveal synthesis of (p)ppGpp by an ATP-GTP 3'-pyrophosphotransferase as well as an ability to degrade (p)ppGpp by a Mn(2+)-dependent 3'-pyrophosphohydrolase. Removal of the C-terminal half-protein has reciprocal regulatory effects on the activities of the N-terminal half-protein. Compared to the full-length protein, deletion activates (p)ppGpp synthesis specific activity about 12-fold and simultaneously inhibits (p)ppGpp degradation specific activity about 150-fold to shift the balance of the two activities in favor of synthesis. Cellular (p)ppGpp accumulation behavior is consistent with these changes. The bifunctional N-terminal half-protein can be further dissected into overlapping monofunctional subdomains, since purified peptides display either degradation activity (residues 1 to 224) or synthetic activity (residues 79 to 385) in vitro. These assignments can also apply to RelA and SpoT. The ability of Rel(Seq) to mediate (p)ppGpp accumulation during amino acid starvation in S. equisimilis is absent when the protein is expressed ectopically in Escherichia coli. Fusing the N-terminal half of Rel(Seq) with the C-terminal domain of RelA creates a chimeric protein that restores the stringent response in E. coli by inhibiting unregulated degradation and restoring regulated synthetic activity. Reciprocal intramolecular regulation of the dual activities may be a general intrinsic feature of Rel/Spo homolog proteins.
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Affiliation(s)
- Undine Mechold
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-2785, USA
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29
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Jordi BJ, Boutaga K, van Heeswijk CM, van Knapen F, Lipman LJ. Sensitivity of Shiga toxin-producing Escherichia coli (STEC) strains for colicins under different experimental conditions. FEMS Microbiol Lett 2001; 204:329-34. [PMID: 11731144 DOI: 10.1111/j.1574-6968.2001.tb10906.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Twenty Escherichia coli strains producing well-characterised colicins were tested for their inhibitory activity against five Shiga toxin-producing E. coli (STEC) strains using different media under aerobic and anaerobic conditions. The five STEC strains used were of serotype O26, O111, O128, O145 and O157:H7 which are frequently isolated serotypes associated with disease in humans. The main route of infection for humans is through the eating of badly cooked or handled beef. The major reservoir for STEC strains in cattle is the rumen. To mimic the situation in the rumen of cattle, overlay assays were also performed under anaerobic conditions in the presence of 30% rumen fluid. Colicins E1, E4, E8-J, K and S4 are most active against STEC strains under anaerobic conditions in the absence or presence of rumen fluid. These colicins will be used in future experiments with the aim to eradicate the presence of STEC in cattle.
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Affiliation(s)
- B J Jordi
- Bacteriology Division, Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands.
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