Leptospira interrogans encodes a canonical BamA and three novel noNterm Omp85 outer membrane protein paralogs.

The Omp85 family of outer membrane proteins are ubiquitously distributed among diderm bacteria and play essential roles in outer membrane (OM) biogenesis. The majority of Omp85 orthologs are bipartite and consist of a conserved OM-embedded 16-stranded beta-barrel and variable periplasmic functional domains. Here, we demonstrate that Leptospira interrogans encodes four distinct Omp85 proteins.

Investigating Additive and Replacing Horizontal Gene Transfers Using Phylogenies and Whole Genomes.

Horizontal gene transfer (HGT) is fundamental to microbial evolution and adaptation. When a gene is horizontally transferred, it may either add itself as a new gene to the recipient genome (possibly displacing nonhomologous genes) or replace an existing homologous gene. Currently, studies do not usually distinguish between "additive" and "replacing" HGTs, and their relative frequencies, integration mechanisms, and specific roles in microbial evolution are poorly understood.

Using the pan-genomic framework for the discovery of genomic islands in the haloarchaeon .

In this study, we use pan-genomics to characterize the genomic variability of the widely dispersed halophilic archaeal species ). We include a multi-regional sampling of newly sequenced, high-quality draft genomes. The pan-genome graph of the species reveals 50 genomic islands that represent rare accessory genetic capabilities available to members.

Neighboring inteins interfere with one another's homing capacity.

Inteins are mobile genetic elements that invade conserved genes across all domains of life and viruses. In some instances, a single gene will have several intein insertion sites. In Haloarchaea, the minichromosome maintenance (MCM) protein at the core of replicative DNA helicase contains four intein insertion sites within close proximity, where two of these sites (MCM-a and MCM-d) are more likely to be invaded.

The Evolutionary History of a DNA Methylase Reveals Frequent Horizontal Transfer and Within-Gene Recombination.

Inteins, often referred to as protein introns, are highly mobile genetic elements that invade conserved genes throughout the tree of life. Inteins have been found to invade a wide variety of key genes within actinophages. While in the process of conducting a survey of these inteins in actinophages, we discovered that one protein family of methylases contained a putative intein, and two other unique insertion elements.

A structural dendrogram of the actinobacteriophage major capsid proteins provides important structural insights into the evolution of capsid stability.

Many double-stranded DNA viruses, including tailed bacteriophages (phages) and herpesviruses, use the HK97-fold in their major capsid protein to make the capsomers of the icosahedral viral capsid. After the genome packaging at near-crystalline densities, the capsid is subjected to a major expansion and stabilization step that allows it to withstand environmental stresses and internal high pressure. Several different mechanisms for stabilizing the capsid have been structurally characterized, but how these mechanisms have evolved is still not understood.

An Efficient, Nonphylogenetic Method for Detecting Genes Sharing Evolutionary Signals in Phylogenomic Data Sets.

Assessing the compatibility between gene family phylogenies is a crucial and often computationally demanding step in many phylogenomic analyses. Here, we describe the Evolutionary Similarity Index (IES), a means to assess shared evolution between gene families using a weighted orthogonal distance regression model applied to sequence distances. The utilization of pairwise distance matrices circumvents comparisons between gene tree topologies, which are inherently uncertain and sensitive to evolutionary model choice, phylogenetic reconstruction artifacts, and other sources of error.

Improving Phylogenies Based on Average Nucleotide Identity, Incorporating Saturation Correction and Nonparametric Bootstrap Support.

Whole-genome comparisons based on average nucleotide identities (ANI) and the genome-to-genome distance calculator have risen to prominence in rapidly classifying prokaryotic taxa using whole-genome sequences. Some implementations have even been proposed as a new standard in species classification and have become a common technique for papers describing newly sequenced genomes. However, attempts to apply whole-genome divergence data to the delineation of higher taxonomic units and to phylogenetic inference have had difficulty matching those produced by more complex phylogenetic methods.

The Evolutionary Origins of Extreme Halophilic Archaeal Lineages.

Interest and controversy surrounding the evolutionary origins of extremely halophilic Archaea has increased in recent years, due to the discovery and characterization of the Nanohaloarchaea and the Methanonatronarchaeia. Initial attempts in explaining the evolutionary placement of the two new lineages in relation to the classical Halobacteria (also referred to as Haloarchaea) resulted in hypotheses that imply the new groups share a common ancestor with the Haloarchaea. However, more recent analyses have led to a shift: the Nanohaloarchaea have been largely accepted as being a member of the DPANN superphylum, outside of the euryarchaeota; whereas the Methanonatronarchaeia have been placed near the base of the Methanotecta (composed of the class II methanogens, the Halobacteriales, and Archaeoglobales).

Systematic Detection of Large-Scale Multigene Horizontal Transfer in Prokaryotes.

Horizontal gene transfer (HGT) is central to prokaryotic evolution. However, little is known about the "scale" of individual HGT events. In this work, we introduce the first computational framework to help answer the following fundamental question: How often does more than one gene get horizontally transferred in a single HGT event? Our method, called HoMer, uses phylogenetic reconciliation to infer single-gene HGT events across a given set of species/strains, employs several techniques to account for inference error and uncertainty, combines that information with gene order information from extant genomes, and uses statistical analysis to identify candidate horizontal multigene transfers (HMGTs) in both extant and ancestral species/strains.

Interaction of two strongly divergent archaellins stabilizes the structure of the Halorubrum archaellum.

Halophilic archaea from the genus Halorubrum possess two extraordinarily diverged archaellin genes, flaB1 and flaB2. To clarify roles for each archaellin, we compared two natural Halorubrum lacusprofundi strains: One of them contains both archaellin genes, and the other has the flaB2 gene only. Both strains synthesize functional archaella; however, the strain, where both archaellins are present, is more motile.

Identification and characterization of putative Aeromonas spp. T3SS effectors.

The genetic determinants of bacterial pathogenicity are highly variable between species and strains. However, a factor that is commonly associated with virulent Gram-negative bacteria, including many Aeromonas spp., is the type 3 secretion system (T3SS), which is used to inject effector proteins into target eukaryotic cells.

The Patchy Distribution of Restriction⁻Modification System Genes and the Conservation of Orphan Methyltransferases in Halobacteria.

Restriction⁻modification (RM) systems in bacteria are implicated in multiple biological roles ranging from defense against parasitic genetic elements, to selfish addiction cassettes, and barriers to gene transfer and lineage homogenization. In bacteria, DNA-methylation without cognate restriction also plays important roles in DNA replication, mismatch repair, protein expression, and in biasing DNA uptake. Little is known about archaeal RM systems and DNA methylation.

Low-Level Antimicrobials in the Medicinal Leech Select for Resistant Pathogens That Spread to Patients.

Fluoroquinolones (FQs) and ciprofloxacin (Cp) are important antimicrobials that pollute the environment in trace amounts. Although Cp has been recommended as prophylaxis for patients undergoing leech therapy to prevent infections by the leech gut symbiont , a puzzling rise in Cp-resistant (Cp) infections has been reported. We report on the effects of subtherapeutic FQ concentrations on bacteria in an environmental reservoir, the medicinal leech, and describe the presence of multiple antibiotic resistance mutations and a gain-of-function resistance gene.

Does Sequence Conservation Provide Evidence for Biological Function?

Finding a signature of purifying selection in a gene is usually interpreted as evidence for the gene providing a function that is targeted by natural selection. This opinion offers a very different hypothesis: purifying selection may be due to removing harmful mutations from the population, that is, the gene and its encoded protein become harmful after a mutation occurred, possibly because the mutated protein interferes with the translation machinery, or because of toxicity of the misfolded protein. Finding a signature of purifying selection should not automatically be considered proof of the gene's selectable function.

Leisingera sp. JC1, a Bacterial Isolate from Hawaiian Bobtail Squid Eggs, Produces Indigoidine and Differentially Inhibits Vibrios.

Female members of many cephalopod species house a bacterial consortium in the accessory nidamental gland (ANG), part of the reproductive system. These bacteria are deposited into eggs that are then laid in the environment where they must develop unprotected from predation, pathogens, and fouling. In this study, we characterized the genome and secondary metabolite production of Leisingera sp.

Impact of a homing intein on recombination frequency and organismal fitness.

Inteins are parasitic genetic elements that excise themselves at the protein level by self-splicing, allowing the formation of functional, nondisrupted proteins. Many inteins contain a homing endonuclease (HEN) domain and rely on its activity for horizontal propagation. However, successful invasion of an entire population will make this activity redundant, and the HEN domain is expected to degenerate quickly under these conditions.

Horizontal gene transfer: building the web of life.

Horizontal gene transfer (HGT) is the sharing of genetic material between organisms that are not in a parent-offspring relationship. HGT is a widely recognized mechanism for adaptation in bacteria and archaea. Microbial antibiotic resistance and pathogenicity are often associated with HGT, but the scope of HGT extends far beyond disease-causing organisms.

Ancient horizontal gene transfer and the last common ancestors.

Background: The genomic history of prokaryotic organismal lineages is marked by extensive horizontal gene transfer (HGT) between groups of organisms at all taxonomic levels. These HGT events have played an essential role in the origin and distribution of biological innovations. Analyses of ancient gene families show that HGT existed in the distant past, even at the time of the organismal last universal common ancestor (LUCA).

Inteins as indicators of gene flow in the halobacteria.

This research uses inteins, a type of mobile genetic element, to infer patterns of gene transfer within the Halobacteria. We surveyed 118 genomes representing 26 genera of Halobacteria for intein sequences. We then used the presence-absence profile, sequence similarity and phylogenies from the inteins recovered to explore how intein distribution can provide insight on the dynamics of gene flow between closely related and divergent organisms.

AST: an automated sequence-sampling method for improving the taxonomic diversity of gene phylogenetic trees.

A challenge in phylogenetic inference of gene trees is how to properly sample a large pool of homologous sequences to derive a good representative subset of sequences. Such a need arises in various applications, e.g.

Distribution and evolution of the mobile vma-1b intein.

Inteins are self-splicing parasitic genetic elements found in all domains of life. These genetic elements are found in highly conserved positions in conserved proteins. One protein family that has been invaded by inteins is the vacuolar and archaeal catalytic ATPase subunits (vma-1).

Reconstruction of ancestral 16S rRNA reveals mutation bias in the evolution of optimal growth temperature in the Thermotogae phylum.

Optimal growth temperature is a complex trait involving many cellular components, and its physiology is not yet fully understood. Evolution of continuous characters, such as optimal growth temperature, is often modeled as a one-dimensional random walk, but such a model may be an oversimplification given the complex processes underlying the evolution of continuous characters. Recent articles have used ancestral sequence reconstruction to infer the optimal growth temperature of ancient organisms from the guanine and cytosine content of the stem regions of ribosomal RNA, allowing inferences about the evolution of optimal growth temperature.