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At least 775 records · Page 43Linked to original sources
PubMed2003

Evolution of cooperation and conflict in experimental bacterial populations.

A fundamental problem in biology is the evolutionary transition from single cells to multicellular life forms. During this transition the unit of selection shifts from individual cells to groups of cooperating cells. Although there is much theory, there are few empirical studies. Here we describe an evolutionary transition that occurs in experimental populations of Pseudomonas fluorescens propagated in a spatially heterogeneous environment. Cooperating groups are formed by over-production of an adhesive polymer, which causes the interests of individuals to align with those of the group. The costs and benefits of cooperation, plus evolutionary susceptibility to defecting genotypes, were analysed to determine conformation to theory. Cooperation was costly to individuals, but beneficial to the group. Defecting genotypes evolved in populations founded by the cooperating type and were fitter in the presence of this type than in its absence. In the short term, defectors sabotaged the viability of the group; but these findings nevertheless show that transitions to higher orders of complexity are readily achievable, provide insights into the selective conditions, and facilitate experimental analysis of the evolution of individuality.

Bacterial Adhesion↗
PubMed1989

Bacterial polysaccharide capsule synthesis, export and evolution of structural diversity.

Elaboration of a capsule composed of one of a range of acidic polysaccharides is a common feature of many bacteria, particularly those capable of causing serious infections in humans. Biochemical and genetical analyses of capsule biogenesis in Escherichia coli are beginning to reveal new aspects of polysaccharide biosynthesis. Genes have been identified which are thought to encode products responsible for the translocation of these high molecular-weight polysaccharides across the cytoplasmic and outer membranes, and the organization of exported polysaccharide into a capsule. Their further analysis should provide new insights into membrane biology, particularly since the genes in question are absent from the often used laboratory strains of E. coli. Genetic analysis of capsule diversity is beginning to suggest possible mechanisms for the generation of the structural diversity of polysaccharides.

Antigens, Bacterial↗
PubMed1980

Evolution in Pseudomonas fluorescens.

The relationships among 93 strains of Pseudomonas fluorescens were investigated by (1) a numerical taxonomic analysis on the results of 150 phenotypic tests, (2) DNA hybridization studies using 16 reference strains, (3) quantitative microcomplement fixation studies using six reference strains with antibodies directed against the protein azurin. In general, the strains fell into distinct clusters. Assignment to these clusters on the basis of azurin immunological similarity showed 98% agreement with assignment based on DNA homology, suggesting that many genes will follow the same pattern. Of the strains that clustered on the basis of genotype (DNA, azurin) 88% also clustered on the basis of phenotype. The occasional noncongruency observed between the genotypic and phenotypic data may be due to the variable rates of phenotypic evolution. These results provide a perspective on the roles of horizontal and vertical transfer of genes in the evolution of this bacterial group.

Azurin↗
PubMed2001

Evolution of a molecular switch: universal bacterial GTPases regulate ribosome function.

The GTPases comprise a protein superfamily of highly conserved molecular switches adapted to many diverse functions. These proteins are found in all domains of life and often perform essential roles in fundamental cellular processes. Analysis of data from genome sequencing projects demonstrates that bacteria possess a core of 11 universally conserved GTPases (elongation factor G and Tu, initiation factor 2, LepA, Era, Obg, ThdF/TrmE, Ffh, FtsY, EngA and YchF). Investigations aimed at understanding the function of GTPases indicate that a second conserved feature of these proteins is that they elicit their function through interaction with RNA and/or ribosomes. An emerging concept suggests that the 11 universal GTPases are either necessary for ribosome function or transmitting information from the ribosome to downstream targets for the purpose of generating specific cellular responses. Furthermore, it is suggested that progenitor GTPases were early regulators of RNA function and may have existed in precursors of cellular systems driven by catalytic RNA. If this is the case, then a corollary of this hypothesis is that GTPases that do not bind RNA arose at a later time from an RNA-binding progenitor that lost the capability to bind RNA.

Bacteria↗
PubMed2000

Population structure and evolutionary dynamics of pathogenic bacteria.

Evidence concerning the significance of recombination within natural bacterial populations has historically come from two main sources: multilocus enzyme electrophoresis (MLEE) and nucleotide sequence data. Here we discuss evidence from a third method, multilocus sequence typing (MLST), which is a development of MLEE based on nucleotide sequencing that combines the advantages of both approaches. MLST has confirmed both the existence of clones and the high rates of recombination for several bacterial pathogens. The data are consistent with "epidemic" population structures, where clones are superimposed upon a backdrop of frequent recombination, thus, in the short term, resisting the homogenising effect of recombination. The nature of the selective advantage of clones, however, and how this advantage relates to virulence are unclear. The current evidence also has broader implications concerning bacterial species definition, the management of antibiotic-resistant bacteria and the assessment of the dangers of releasing genetically modified organisms into the environment.

Bacteria↗
PubMed1984

Evolutionary relationships of the Bacillus licheniformis macrolide-lincosamide-streptogramin B resistance elements.

Naturally occurring erythromycin (Em) resistance was found in 11 of the 18 Bacillus licheniformis isolates tested but was absent from a wide variety of other Bacillus strains. The Em resistance elements confer inducible macrolide-lincosamide-streptogramin B (MLS) resistance and are related to ermD , an MLS resistance element previously cloned from the chromosome of B. licheniformis 749. The MLS sensitive B. licheniformis strains and the other sensitive Bacillus strains tested, lack sequences with detectable homology to ermD . The sensitive B. licheniformis strains do exhibit homology to sequences which flank ermD in B. licheniformis 749. The relative sizes of the homologous DNA fragments suggest that the sensitive strains are lacking a 3.6 kb segment which contains ermD . It is shown that ermD is homologous to chromosomal DNA from Streptomyces erythreus ATCC 11635, an Em producing organism. These observations suggest to us that MLS resistance may have arisen in the Streptomyces and spread to B. licheniformis, another gram positive bacterium found in soil. It is further proposed that ermD is or was located on a transposon-like element and has spread and evolved further to yield a variety of related Staphylococcal and Streptococcal MLS determinants.

Anti-Bacterial Agents↗
PubMed1997

Molecular phylogenetic characterization of Streptomyces protease inhibitor family.

We previously found that proteinaceous protease inhibitors homologous to Streptomyces subtilisin inhibitor (SSI) are widely produced by various Streptomyces species, and we designated them "SSI-like proteins" (Taguchi S, Kikuchi H, Suzuki M, Kojima S, Terabe M, Miura K, Nakase T, Momose H [1993] Appl Environ Microbiol 59:4338-4341). In this study, SSI-like proteins from five strains of the genus Streptoverticillium were purified and sequenced, and molecular phylogenetic trees were constructed on the basis of the determined amino acid sequences together with those determined previously for Streptomyces species. The phylogenetic trees showed that SSI-like proteins from Streptoverticillium species are phylogenetically included in Streptomyces SSI-like proteins but form a monophyletic group as a distinct lineage within the Streptomyces proteins. This provides an alternative phylogenetic framework to the previous one based on partial small ribosomal RNA sequences, and it may indicate that the phylogenetic affiliation of the genus Streptoverticillium should be revised. The phylogenetic trees also suggested that SSI-like proteins possessing arginine or methionine at the P1 site, the major reactive center site toward target proteases, arose multiple times on independent lineages from ancestral proteins possessing lysine at the P1 site. Most of the codon changes at the P1 site inferred to have occurred during the evolution of SSI-like proteins are consistent with those inferred from the extremely high G + C content of Streptomyces genomes. The inferred minimum number of amino acid replacements at the P1 site was nearly equal to the average number for all the variable sites. It thus appears that positive Darwinian selection, which has been postulated to account for accelerated rates of amino acid replacement at the major reaction center site of mammalian protease inhibitors, may not have dictated the evolution of the bacterial SSI-like proteins.

Amino Acid Sequence↗
PubMed2006

Gliding motility: anticipating the next move with a molecular clock.

FrzS protein is important for normal social motility in myxobacteria, which includes periodic reversals in the direction of cell motion. Recent results show that cell reversal correlates with the migration of FrzS from the old leading pole of the cell to the new leading pole.

Bacterial Proteins↗
PubMed2004

Population structure of pathogenic bacteria revisited.

This minireview summarizes the historical development of bacterial population genetic concepts since the early 1980s. Initially multilocus enzyme electrophoresis was used to determine population structures but this technique is poorly portable between laboratories and was replaced in 1998 by multilocus sequence typing. Diverse population structures exist in different bacterial species. Two distinctive structures are described in greater detail. "Young" organisms, such as Yersinia pestis, have evolved or undergone a severe bottleneck in recent millennia and have not yet accumulated much sequence diversity. "genoclouds" in subgroup III Neisseria meningitidis arise because of the accumulation of diversity due to herd immunity, which is then purified during subsequent epidemic spread.

Bacteria↗
PubMed2001

Size matters?

Explore the source record for details and available documents.

Bacterial Proteins↗
PubMedDate not supplied

Two contrary modes of chemolithotrophy in the same archaebacterium.

Sulphur-dependent archaebacteria, which are found around nearly boiling continental solfataric springs and mud holes, can be assigned to two distinct branches: the aerobic, sulphur-oxidizing Sulfolobales and the strictly anaerobic sulphur-reducing Thermoproteales. Here, we report the isolation of a group of extremely thermophilic solfataric archaebacteria that are able to grow either strictly anaerobically by reduction, or fully aerobically by oxidation of molecular sulphur, depending on the oxygen supply. We have also established that the ability to grow in these two ways is shared by Sulfolobus brierleyi, a well-known less thermophilic sulphur-oxidizing archaebacterium capable of ore-leaching. The phenomenon may be dependent on a fundamental switch in genome expression. These organisms might represent the primitive fore-runners of sulphur-oxidizing archaebacteria, meeting their energy requirements either by oxidation or by reduction of the same element.

Archaea↗
PubMed2004

Analysis of Rhizobium etli and of its symbiosis with wild Phaseolus vulgaris supports coevolution in centers of host diversification.

Common beans (Phaseolus vulgaris) comprise three major geographic genetic pools, one in Mexico, Central America, and Colombia, another in the southern Andes, and a third in Ecuador and northern Peru. Species Rhizobium etli is the predominant rhizobia found symbiotically associated with beans in the Americas. We have found polymorphism in the common nodulation gene nodC among R. etli strains from a wide range of geographical origins, which disclosed three nodC types. The different nodC alleles in American strains show varying predominance in their regional distributions in correlation with the centers of bean genetic diversification (BD centers). By cross-inoculating wild common beans from the three BD centers with soils from Mexico, Ecuador, Bolivia, and Northwestern Argentina, the R. etli populations from nodules originated from Mexican soil again showed allele predominance that was opposite to those originated from Bolivian and Argentinean soil, whereas populations from Ecuadorian soil were intermediate. These results also indicated that the preferential nodulation of beans by geographically related R. etli lineages was independent of the nodulating environment. Coinoculation of wild common beans from each of the three BD centers with an equicellular mixture of R. etli strains representative of the Mesoamerican and southern Andean lineages revealed a host-dependent distinct competitiveness: beans from the Mesoamerican genetic pool were almost exclusively nodulated by strains from their host region, whereas nodules of beans from the southern Andes were largely occupied by the geographically cognate R. etli lineages. These results suggest coevolution in the centers of host genetic diversification.

Acyltransferases↗
PubMed2004

Microevolution and history of the plague bacillus, Yersinia pestis.

The association of historical plague pandemics with Yersinia pestis remains controversial, partly because the evolutionary history of this largely monomorphic bacterium was unknown. The microevolution of Y. pestis was therefore investigated by three different multilocus molecular methods, targeting genomewide synonymous SNPs, variation in number of tandem repeats, and insertion of IS100 insertion elements. Eight populations were recognized by the three methods, and we propose an evolutionary tree for these populations, rooted on Yersinia pseudotuberculosis. The tree invokes microevolution over millennia, during which enzootic pestoides isolates evolved. This initial phase was followed by a binary split 6,500 years ago, which led to populations that are more frequently associated with human disease. These populations do not correspond directly to classical biovars that are based on phenotypic properties. Thus, we recommend that henceforth groupings should be based on molecular signatures. The age of Y. pestis inferred here is compatible with the dates of historical pandemic plague. However, it is premature to infer an association between any modern molecular grouping and a particular pandemic wave that occurred before the 20th century.

Animals↗
PubMed2005

Nucleoid remodeling by an altered HU protein: reorganization of the transcription program.

Bacterial nucleoid organization is believed to have minimal influence on the global transcription program. Using an altered bacterial histone-like protein, HUalpha, we show that reorganization of the nucleoid configuration can dynamically modulate the cellular transcription pattern. The mutant protein transformed the loosely packed nucleoid into a densely condensed structure. The nucleoid compaction, coupled with increased global DNA supercoiling, generated radical changes in the morphology, physiology, and metabolism of wild-type K-12 Escherichia coli. Many constitutive housekeeping genes involved in nutrient utilization were repressed, whereas many quiescent genes associated with virulence were activated in the mutant. We propose that, as in eukaryotes, the nucleoid architecture dictates the global transcription profile and, consequently, the behavior pattern in bacteria.

Bacterial Proteins↗
PubMed1990

A single clone of Staphylococcus aureus causes the majority of cases of toxic shock syndrome.

Genetic relationships among 315 isolates of the bacterium Staphylococcus aureus expressing toxic shock syndrome toxin-1 (TSST-1) recovered primarily from humans with toxic shock syndrome (TSS) in five countries on two continents were determined by analyzing electrophoretically demonstrable allelic variation at 20 chromosomal enzyme loci. Forty-nine distinctive electrophoretic types (ETs), representing multilocus enzyme genotypes, were identified. Cluster analysis of the ETs revealed two major phylogenetic divisions separated at a genetic distance of 0.35 and seven branches diverging from one another at distances greater than or equal to 0.20. A single clone (ET 41) accounted for 88% of cases of TSS with a female urogenital focus and 53% of TSS cases involving nonurogenital (predominantly wound) infections. With few exceptions, strains representing different phylogenetic lines had characteristic TSST-1 gene (tst) restriction fragment length polymorphism patterns obtained by digestion of genomic DNA with Cla I. Strains recovered from ovine and bovine hosts with mastitis were genotypically distinct from the major human TSS clone. The expression of TSST-1 in cell lineages representing the total breadth of multilocus genotypic diversity in the species S. aureus as a whole is interpreted as evidence that the TSST-1 gene is evolutionarily old. The recovery of a single clone from the majority of individuals afflicted with TSS having a urogenital focus and from the genital tract of a large proportion of asymptomatic female carriers strongly suggests that this clone is especially well adapted for colonization of these anatomic sites.

Animals↗