Dataset Information

Bacteriophage-mediated competition in Bordetella bacteria.

ABSTRACT: Apparent competition between species is believed to be one of the principal driving forces that structure ecological communities, although the precise mechanisms have yet to be characterized. Here we develop a model system that isolates phage-mediated interactions by neutralizing resource competition with a large excess of nutrients, and consists of two genetically identical Bordetella strains that differ only in that one is the carrier of phage and the other is susceptible to the phage. We observe and quantify the competitive advantage of the bacterial strain bearing the prophage in both invading and in resisting invasion by the bacterial strain sensitive to the phage, and use our experimental measurements to develop a mathematical model of phage-mediated competition. The model predicts, and experimental evidence confirms, that the competitive advantage conferred by the lysogenic phage depends only on the phage pathology on the sensitive bacterial strain and is independent of other phage and host parameters, such as the infection-causing contact rate, the spontaneous and infection-induced lysis rates and the phage burst size. This work combines experimental and mathematical approaches to the study of phage-driven competition, and provides an experimentally tested framework for evaluation of the effects of pathogens/parasites on interspecific competition.

SUBMITTER: Joo J

PROVIDER: S-EPMC1634791 | biostudies-literature | 2006 Jul

REPOSITORIES: biostudies-literature

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Bacteriophage-mediated competition in Bordetella bacteria.

Joo Jaewook J Gunny Michelle M Cases Marisa M Hudson Peter P Albert Réka R Harvill Eric E

Proceedings. Biological sciences 20060701 1595

Apparent competition between species is believed to be one of the principal driving forces that structure ecological communities, although the precise mechanisms have yet to be characterized. Here we develop a model system that isolates phage-mediated interactions by neutralizing resource competition with a large excess of nutrients, and consists of two genetically identical Bordetella strains that differ only in that one is the carrier of phage and the other is susceptible to the phage. We obse ...[more]

PMID: 16790419

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Project description:Resources available in the human nasal cavity are limited. Therefore, to successfully colonize the nasal cavity, bacteria must compete for scarce nutrients. Competition may occur directly through interference (e.g., antibiotics) or indirectly by nutrient sequestration. To investigate the nature of nasal bacterial competition, we performed coculture inhibition assays between nasal Actinobacteria and Staphylococcus spp. We found that isolates of coagulase-negative staphylococci (CoNS) were sensitive to growth inhibition by Actinobacteria but that Staphylococcus aureus isolates were resistant to inhibition. Among Actinobacteria, we observed that Corynebacterium spp. were variable in their ability to inhibit CoNS. We sequenced the genomes of 10 Corynebacterium species isolates, including 3 Corynebacterium propinquum isolates that strongly inhibited CoNS and 7 other Corynebacterium species isolates that only weakly inhibited CoNS. Using a comparative genomics approach, we found that the C. propinquum genomes were enriched in genes for iron acquisition and harbored a biosynthetic gene cluster (BGC) for siderophore production, absent in the noninhibitory Corynebacterium species genomes. Using a chrome azurol S assay, we confirmed that C. propinquum produced siderophores. We demonstrated that iron supplementation rescued CoNS from inhibition by C. propinquum, suggesting that inhibition was due to iron restriction through siderophore production. Through comparative metabolomics and molecular networking, we identified the siderophore produced by C. propinquum as dehydroxynocardamine. Finally, we confirmed that the dehydroxynocardamine BGC is expressed in vivo by analyzing human nasal metatranscriptomes from the NIH Human Microbiome Project. Together, our results suggest that bacteria produce siderophores to compete for limited available iron in the nasal cavity and improve their fitness.IMPORTANCE Within the nasal cavity, interference competition through antimicrobial production is prevalent. For instance, nasal Staphylococcus species strains can inhibit the growth of other bacteria through the production of nonribosomal peptides and ribosomally synthesized and posttranslationally modified peptides. In contrast, bacteria engaging in exploitation competition modify the external environment to prevent competitors from growing, usually by hindering access to or depleting essential nutrients. As the nasal cavity is a nutrient-limited environment, we hypothesized that exploitation competition occurs in this system. We determined that Corynebacterium propinquum produces an iron-chelating siderophore, and this iron-sequestering molecule correlates with the ability to inhibit the growth of coagulase-negative staphylococci. Furthermore, we found that the genes required for siderophore production are expressed in vivo Thus, although siderophore production by bacteria is often considered a virulence trait, our work indicates that bacteria may produce siderophores to compete for limited iron in the human nasal cavity.

Dataset Information

Bacteriophage-mediated competition in Bordetella bacteria.

Publications

Bacteriophage-mediated competition in Bordetella bacteria.

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