Background Twelve populations of the bacterium, Escherichia coli, adapted to a simple, glucose-limited, laboratory environment over 10,000 generations. As a consequence, these populations tended to lose functionality on alternative resources. I examined whether these populations in turn became inferior competitors in four alternative environments. These experiments are among the first to quantify and compare dimensions of the fundamental and realized niches. Results Three clones were isolated from each of the twelve populations after 10,000 generations of evolution. Direct competition between these clones and the ancestor in the selective environment revealed average fitness improvements of ~50%. When grown in the wells of Biolog plates, however, evolved clones grew 25% worse on average than the ancestor on a variety of different carbon sources. Next, I competed each evolved population versus the ancestor in four foreign environments (10-fold higher and lower glucose concentration, added bile salts, and dilute LB media). Surprisingly, nearly all populations were more fit than the ancestor in each foreign environment, though the margin of improvement was least in the most different environment. Most populations also evolved increased sensitivity to novobiocin. Conclusions Reduced functionality on numerous carbon sources suggested that the fundamental niche of twelve E. coli populations had narrowed after adapting to a specific laboratory environment. However, in spite of these results, the same populations were competitively superior in four novel environments. These findings suggest that adaptation to certain dimensions of the environment may compensate for other functional losses and apparently enhance the realized niche.

Background Laboratory experiments under controlled conditions during thousands of generations are useful tools to assess the processes underlying bacterial evolution. As a result of these experiments, the way in which the traits change in time is obtained. Under these conditions, the bacteria E. coli shows a parallel increase in cell volume and fitness. Results To explain this pattern it is required to consider organismic and population contributions. For this purpose we incorporate relevant information concerning bacterial structure, composition and transformations in a minimal modular model. In the short time scale, the model reproduces the physiological responses of the traits to changes in nutrient concentration. The decay of unused catabolic functions, found experimentally, is introduced in the model using simple population genetics. The resulting curves representing the evolution of volume and fitness in time are in good agreement with those obtained experimentally. Conclusions This study draws attention on physiology when studying evolution. Moreover, minimal modular models appear to be an adequate strategy to unite these barely related disciplines of biology.

Background Insertion Sequence (IS) elements are mobile genetic elements widely distributed among bacteria. Their activities cause mutations, promoting genetic diversity and sometimes adaptation. Previous studies have examined their copy number and distribution in Escherichia coli K-12 and natural isolates. Here, we map most of the IS elements in E. coli B and compare their locations with the published genomes of K-12 and O157:H7. Results The genomic locations of IS elements reveal numerous differences between B, K-12, and O157:H7. IS elements occur in hok-sok loci (homologous to plasmid stabilization systems) in both B and K-12, whereas these same loci lack IS elements in O157:H7. IS elements in B and K-12 are often found in locations corresponding to O157:H7-specific sequences, which suggests IS involvement in chromosomal rearrangements including the incorporation of foreign DNA. Some sequences specific to B are identified, as reported previously for O157:H7. The extent of nucleotide sequence divergence between B and K-12 is <2% for most sequences adjacent to IS elements. By contrast, B and K-12 share only a few IS locations besides those in hok-sok loci. Several phenotypic features of B are explained by IS elements, including differential porin expression from K-12. Conclusions These data reveal a high level of IS activity since E. coli B, K-12, and O157:H7 diverged from a common ancestor, including IS association with deletions and incorporation of horizontally acquired genes as well as transpositions. These findings indicate the important role of IS elements in genome plasticity and divergence.

Background Very small genomes have evolved repeatedly in eubacterial lineages that have adopted obligate associations with eukaryotic hosts. Complete genome sequences have revealed that small genomes retain very different gene sets, raising the question of how final genome content is determined. To examine the process of genome reduction, the tiny genome of the endosymbiont Buchnera aphidicola was compared to the larger ancestral genome, reconstructed on the basis of the phylogenetic distribution of gene orthologs among fully sequenced relatives of Escherichia coli and Buchnera. Results The reconstructed ancestral genome contained 2,425 open reading frames (ORFs). The Buchnera genome, containing 564 ORFs, consists of 153 fragments of 1-34 genes that are syntenic with reconstructed ancestral regions. On the basis of this reconstruction, 503 genes were eliminated within syntenic fragments, and 1,403 genes were lost from the gaps between syntenic fragments, probably in connection with genome rearrangements. Lost regions are sometimes large, and often span functionally unrelated genes. In addition, individual genes and regulatory regions have been lost or eroded. For the categories of DNA repair genes and rRNA genes, most lost loci fall in regions between syntenic fragments. This history of gene loss is reflected in the sequences of intergenic spacers at positions where genes were once present. Conclusions The most plausible interpretation of this reconstruction is that Buchnera lost many genes through the fixation of large deletions soon after the acquisition of an obligate endosymbiotic lifestyle. An implication is that final genome composition may be partly the chance outcome of initial deletions and that neighboring genes influence the likelihood of loss of particular genes and pathways.

Background Infections of bacterial cultures by bacteriophages are serious problems in biotechnological laboratories. Apart from such infections, prophage induction in the host cells may also be dangerous. Escherichia coli is a commonly used host in biotechnological production, and many laboratory strains of this bacterium harbour lambdoid prophages. These prophages may be induced under certain conditions leading to phage lytic development. This is fatal for further cultivations as relatively low, though still significant, numbers of phages may be overlooked. Thus, subsequent cultures of non-lysogenic strains may be infected and destroyed by such phage. Results Here we report that slow growth of bacteria decreases deleterious effects of spontaneous lambdoid prophage induction. Moreover, replacement of glucose with glycerol in a medium stimulates lysogenic development of the phage after infection of E. coli cells. A plasmid was constructed overexpressing the phage 434 cI gene, coding for the repressor of phage promoters which are necessary for lytic development. Overproduction of the cI repressor abolished spontaneous induction of the λimm434 prophage. Conclusions Simple procedures that alleviate problems with spontaneous induction of lambdoid prophage and subsequent infection of E. coli strains by these phages are described. Low bacterial growth rate, replacement of glucose with glycerol in a medium and overproduction of the cI repressor minimise the risk of prophage induction during cultivation of lysogenic bacteria and subsequent infection of other bacterial strains.

The data is in the form of genomic sequences deposited in a public database, growth curves, and bioinformatic analysis of sequences. This dataset is associated with the following publication: Henson, M., J. Santodomingo , P. Kourtev, R. Jensen, and D. Learman. Metabolic and genomic analysis elucidates strain-level variation in Microbacterium spp. isolated from chromate contaminated sediment. PeerJ. PeerJ Inc., Corte Madera, CA, USA, e1395, (2015).

The MARS500 project the longest ground-based space simulation ever provided us with a unique opportunity to trace the crew microbiota over 520 days of isolated confinement such as that faced by astronauts in real long-term interplanetary space flights and after returning to regular life for a total of 2 years.

,Escherichia coli survival in soils containing either composted poultry litter (CPL), heat-treated poultry pellets (HTPP), poultry litter (PL) or unamended (chemical fertilizer). Test plots were either covered with plastic mulch (M) or not mulched (NoM). The study was conducted in 2018 and 2019 during cucumber growing seasons at the University of Delaware research farm and each study lasted 120 days. Data from the current study were collected to examine the survival of non-pathogenic Escherichia coli and transfer to cucumbers grown in same field in two separate years. Soil moisture, total nitrogen, nitrate, total carbon, soluble carbon, soluble solids, rainfall, soil temperature and air temperature, along with the number of days needed for E. coli to decline by 4 log CFU/gdw, were included in random forest models used to a) predict 4-log declines of E. coli inoculated to soils and b) transfer of E. coli to cucumbers from soils with different biological soil amendments. The data included here are specifically for other investigators to use to make different forms or versions of three different statistical models used in the submitted manuscript. Data for three models are included: 1) Dpi4log, the number of days needed for E. coli levels in various combinations of year, amendment and mulch, were calculated by applying sigmoidal (single, double, triple, or quadruple) model to E. coli data collected over time. 2) A random forest model using soil and weather data was used to determine which factors listed above best predicted dpi4log values. This model accounted for 98% of the observed variance. 3) A random forest model using soil and weather data, along with dpi4log, was used to predict transfer of E. coli to soils from cucumbers (log MPN/cucumber). This model accounted for approximately 63% of the variance in the study.,,

,Using the SHIME (an in vitro simulator of the human gut microbiome) we tracked the fate of the probiotic Lacticaseibacillus rhamnosus GG (LGG) over time and across colonic regions. Using fecal inoculum from three healthy human donors, reactors were established representing three colonic regions and both the luminal and mucosal microbiome in those regions. Community composition before, during, and after inoculation of the reactors with LGG as well as short chain fatty acid concentrations representing microbiome metabolic outputs. This dataset includes short-chain fatty acid concentrations and qPCR-based cell concentrations. Raw 16S rRNA amplicon sequencing of the V1-V2 regions can be found in the NCBI Sequence Read Archive associated with BioProject PRJNA893635: https://www.ncbi.nlm.nih.gov/bioproject/PRJNA893635.,Resources in this dataset:,