Mutualistic interaction between Salmonella enterica and Aspergillus niger and its effects on Zea mays colonization.
Bottom Line: Aspergillus niger is a ubiquitous fungus that can often be found in soil or associated to plants and microbial consortia.In this work, we have found that this interaction is stable for weeks without a noticeable negative effect on either organism.Strikingly, co-colonization also causes a reduction in plant invasion by S. Typhimurium.
Affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, HIM building, Room #1042, Boston, MA, 02115, USA.Show MeSH
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Mentions: Because S. Typhimurium is found associated with the fungal hyphae within minutes of co-inoculation, we hypothesized that the bacteria might be using directed motility and chemotaxis (Krell et al., 2011) to move towards the fungus. To test if motility and chemotaxis were involved in the initial attraction of bacteria to the fungus, we performed competition experiments where we analysed attachment of wild-type bacteria compared with either a motility mutant that completely lacks flagella (fliGHI) or a mutant that can swim, but is defective in chemotaxis (cheY). Competition between two differentially labelled wild-type strains was used as a control. When wild-type cells were challenged against each other the competition index was 1, which is what would be expected if equivalent numbers of each strain attached to the fungi (Fig. 2). The ability to swim was essential for fungal colonization by S. Typhimurium as the mutant without flagella was decreased to only 5% of the attached population when competed with the wild type. The chemotaxis mutant also showed a defect, although not as pronounced; the cheY mutant showed a 40% reduction in the attachment to the fungus with respect to the wild type (Fig. 2). These results indicate that S. Typhimurium must be able to swim directionally towards the fungus in order for colonization to occur and the bacterial cells are able to sense the fungus in order to actively move towards it. All in all these results suggest that the interaction is specific.
Affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, HIM building, Room #1042, Boston, MA, 02115, USA.