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Abstract:
The bacterial genus Sphingomonas from the class Alphaproteobacteria is common on leaves and roots of a wide variety of plants, and is widespread in soil and water. However, despite high abundances little is known, in contrast to the (in)famous abundant genus Pseudomonas, with which its name rhymes. Analyzing the genomes of over 400 plant-associated Sphingomonas reveals an arsenal of genes for biotic interactions and great genomic diversity, especially compared to Pseudomonas isolated from the same plants. As there are no important Sphingomonas plant pathogens, such genes are presumably either involved in positive interactions with the plant or interactions with other microbes. Some Sphingomonas, including some of our isolates, can protect against bacterial and fungal pathogens, and others are reported to promote plant growth through other means. Fascinatingly, Sphingomonas seem to rely on healthy plant cells for their success, as they are quickly outcompeted in injured plant tissue. Using a subset of isolates from which we have closed the genomes, we are undertaking in my new group a deeper study of the genes involved in association with plants using experimental mutant screens, studying bacterial transcription in various environments, and characterizing its namesake sphingolipids that replace lipopolysaccharides to comprise its outer cell membrane.
