Marcos Peñalver, Alberto Paradela, César Palacios-Cuéllar, M. Graciela Pucciarelli, Francisco García-del Portillo
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引用次数: 0
Abstract
The Candidate Phyla Radiation (CPR) encompasses widespread uncultivated bacteria with reduced genomes and limited metabolic capacities. Most CPR bacteria lack the minimal set of enzymes required for peptidoglycan (PG) synthesis, leaving it unclear how these bacteria produce this essential envelope component. In this study, we analysed the distribution of d-amino acid racemases that produce the universal PG components d-glutamate (d-Glu) or d-alanine (d-Ala). We also examined moonlighting enzymes that synthesize d-Glu or d-Ala. Unlike other phyla in the domain Bacteria, CPR bacteria do not exhibit these moonlighting activities and have, at most, one gene encoding either a Glu or Ala racemase. One of these ‘orphan’ racemases is a predicted Glu racemase (MurICPR) from the CPR bacterium Candidatus Saccharimonas aalborgenesis. The expression of MurICPR restores the growth of a Salmonellad-Glu auxotroph lacking its endogenous racemase and results in the substitution of l-Ala by serine as the first residue in a fraction of the PG stem peptides. In vitro, MurICPR exclusively racemizes Glu as a substrate. Therefore, Ca. Saccharimonas aalborgensis may couple Glu racemization to serine and d-Glu incorporation into the stem peptide. Our findings provide the first insights into the synthesis of PG by an uncultivated environmental bacterium and illustrate how to experimentally test enzymatic activities from CPR bacteria related to PG metabolism.
期刊介绍:
Environmental Microbiology provides a high profile vehicle for publication of the most innovative, original and rigorous research in the field. The scope of the Journal encompasses the diversity of current research on microbial processes in the environment, microbial communities, interactions and evolution and includes, but is not limited to, the following:
the structure, activities and communal behaviour of microbial communities
microbial community genetics and evolutionary processes
microbial symbioses, microbial interactions and interactions with plants, animals and abiotic factors
microbes in the tree of life, microbial diversification and evolution
population biology and clonal structure
microbial metabolic and structural diversity
microbial physiology, growth and survival
microbes and surfaces, adhesion and biofouling
responses to environmental signals and stress factors
modelling and theory development
pollution microbiology
extremophiles and life in extreme and unusual little-explored habitats
element cycles and biogeochemical processes, primary and secondary production
microbes in a changing world, microbially-influenced global changes
evolution and diversity of archaeal and bacterial viruses
new technological developments in microbial ecology and evolution, in particular for the study of activities of microbial communities, non-culturable microorganisms and emerging pathogens