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 Experimental populations of Escherichia coli have evolved for 20,000 generations in a uniform environment. Their rate of improvement, as measured in competitions with the ancestor in that environment, has declined substantially over this period. This deceleration has been interpreted as the bacteria approaching a peak or plateau in a fitness landscape. Alternatively, this deceleration might be caused by non-transitive competitive interactions, in particular such that the measured advantage of later genotypes relative to earlier ones would be greater if they competed directly. Results To distinguish these two hypotheses, we performed a large set of competitions using one of the evolved lines. Twenty-one samples obtained at 1,000-generation intervals each competed against five genetically marked clones isolated at 5,000-generation intervals, with three-fold replication. The pattern of relative fitness values for these 315 pairwise competitions was compared with expectations under transitive and non-transitive models, the latter structured to produce the observed deceleration in fitness relative to the ancestor. In general, the relative fitness of later and earlier generations measured by direct competition agrees well with the fitness inferred from separately competing each against the ancestor. These data thus support the transitive model. Conclusion Non-transitive competitive interactions were not a major feature of evolution in this population. Instead, the pronounced deceleration in its rate of fitness improvement indicates that the population early on incorporated most of those mutations that provided the greatest gains, and subsequently relied on beneficial mutations that were fewer in number, smaller in effect, or both.

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.

These data include detailed sample description (sampling locations, sampling events, DNA concentrations in four separate spreadsheet in an Excel file) and DNA sequencing plate layout. This dataset is associated with the following publication: Li, L., D. Ning, Y. Jeon, H. Ryu, J. SantoDomingo, D. Kang, A. Kadudula, and Y. Seo. Ecological Insights into Assembly Processes and Network Structures of Bacterial Biofilms in Full-scale Biologically Active Carbon Filters under Ozone Implementation. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 751: 141409, (2021).

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).

This repository includes the raw data, analysis code, and results of a systematic analysis of natural transformation (i.e., horizontal gene transfer; HGT) of bacteria in a naturally occurring microbiome (human stool) following exposure to free extracellular DNA (eDNA) that coded for antibiotic resistance. A full description of this effort is available in the associated publication.

Bacterial behavior has been observed to change during spaceflight. Higher final cell counts enhanced biofilm formation increased virulence and reduced susceptibility to antibiotics have been reported to occur for cells cultured in space . Most of these phenomena are theorized as being an indirect effect of an altered extracellular environment where the carbon source uptake is inhibited and excreted acidic byproducts buildup around the cell due to the lack of gravity-driven transport forces. However to date neither spaceflight results ground-based studies physical measurement techniques nor computational approaches have provided sufficient evidence needed to confirm this model. Gene expression data from the Antibiotic Effectiveness in Space (AES-1) experiment however have now allowed us to look into the biomolecular processes behind these observations and showed a systematic activation of glucose starvation and acid resistance genes. These results corroborate the reduced mass transport model proposed to govern bacterial responses to spaceflight. Furthermore the gene expression data suggests that metabolism was stimulated in space which could play a role in causing the observed increase in bacterial cell concentrations in microgravity. Similarly the decrease in extracellular pH may also be involved with the reported increase in virulence in space.

Bacterial behavior has been observed to change during spaceflight. Higher final cell counts enhanced biofilm formation increased virulence and reduced susceptibility to antibiotics have been reported to occur for cells cultured in space . Most of these phenomena are theorized as being an indirect effect of an altered extracellular environment where the carbon source uptake is inhibited and excreted acidic byproducts buildup around the cell due to the lack of gravity-driven transport forces. However to date neither spaceflight results ground-based studies physical measurement techniques nor computational approaches have provided sufficient evidence needed to confirm this model. Gene expression data from the Antibiotic Effectiveness in Space (AES-1) experiment however have now allowed us to look into the biomolecular processes behind these observations and showed a systematic activation of glucose starvation and acid resistance genes. These results corroborate the reduced mass transport model proposed to govern bacterial responses to spaceflight. Furthermore the gene expression data suggests that metabolism was stimulated in space which could play a role in causing the observed increase in bacterial cell concentrations in microgravity. Similarly the decrease in extracellular pH may also be involved with the reported increase in virulence in space.