Multilevel populations and the evolution of antibiotic resistance through horizontal gene transfer

Abstract

Horizontal gene transfer (HGT) can create diversity in the genetic repertoire of a lineage. Successful gene transfer likely occurs more frequently between more closely related organisms, leading to the formation of higher-level exchange groups that in some respects are comparable to single-species populations. Genes that appear fixed in a single species can be replaced through distant homologs or iso-functional analogs acquired through HGT. These genes may originate from other species or they may be acquired by an individual strain from the species pan-genome. Because of their similarity to alleles in a population, we label these gene variants that are exchanged between related species as homeoalleles. In a case study, we show that biased gene transfer plays an important role in the evolution of aminoacyl-tRNA synthetases (aaRS). Many microorganisms make use of these genes against naturally occurring antibiotics. We suggest that the resistance against naturally occurring antibiotics is the likely driving force behind the frequent switching between divergent aaRS types and the reason for the maintenance of these homeoalleles in higher-level exchange groups. Resistance to naturally occurring antibiotics may lead to the maintenance of different types of aminoacyl-tRNA synthetases in Bacteria through gene transfer.

Molecular Evolution of Aminoacyl tRNA Synthetase Proteins in the Early History of Life

“…Conveniently, as the ancestral reconstructions of gene families are independent of organismal history, these reticulations have little effect on inferring deep ancestral states of synthetase families. In fact, reconstruction of homeoallele ancestors may even elucidate the selective forces at work behind their divergence (Andam et al 2011). Homeoalleles are divergent enzymes of identical functions, which are transferred within higherlevel exchange groups, such as class or phylum (Andam et al 2010;Andam and Gogarten 2011a).…”

Accelerated Reduction of Chlorinated Nitroaromatic Antibiotic Chloramphenicol by Biocathode

“…1,2 The chlorinated nitroaromatic antibiotic chloramphenicol (CAP) (2,2-dichloro-N-[(1R,2R)-2-hydroxy-1-(hydroxymethyl)-2-(4-nitrophenyl) ethyl] acetamide) was introduced into clinical practice in 1949 and also the first synthetic antibiotic to be applied at large scale, 3 serving as an effective bacteriostatic antimicrobial to many Gram-positive and Gram-negative bacteria, including most anaerobic organisms. However, owing to the fatal toxicity of CAP to aplastic anemia and the potential carcinogenicity and genotoxicity of CAP to humans, 3,4 the U.S. Food and Drug Administration banned its use on food-producing animals.…”

Insights into the metabolism, lifestyle and putative evolutionary history of the novel archaeal phylum ‘Diapherotrites’

“…Although the role of HGT in conferring specific capabilities to recipient prokaryotic species, for example, antibiotic resistance or heavy metal resistance (Andam et al, 2011;Navarro et al, 2013), has long been recognized, the impact of HGT on prokaryotic evolutionary history and its potential role in organismal transition to new habitats and lifestyles has received less attention. The acquisition of bacterial genes was recently proposed as a driver of Halobacteriales evolution from a methanogenic ancestor (Nelson-Sathi et al, 2012).…”