An important factor dictating coral fitness is the quality of bacteria associated with corals and coral reefs. One way that bacteria benefit corals is by stimulating the larval to juvenile life cycle transition of settlement and metamorphosis. Tetrabromopyrrole (TBP) is a small molecule produced by bacteria that stimulates metamorphosis with and without attachment in a range of coral species. A standing debate remains, however, about whether TBP biosynthesis from live
Rhizobium sp. IRBG74 is a nitrogen-fixing symbiont of Sesbania cannabina and a growth-promoting endophyte of rice, thus making it a good model to compare rhizobial interactions with legumes and cereals. In this report, we show that Rhizobium sp. IRBG74 forms biofilms on the roots of S. cannabina and rice. A mutant defective in biofilm formation was identified by screening a transposon mutant library. The transposon insertion was in thiQ, part of the thiBPQ operon that encodes the components of a thiamine/thiamine pyrophosphate ABC transporter. Complementation with thiBPQ partially restored biofilm formation. Addition of thiamine in growth media led to repression of thiC expression in the wild-type strain but not in the thiQ mutant. These results suggest that thiBPQ is involved in thiamine/TPP transport in Rhizobium sp. IRBG74. Using a GUS reporter, we show that the expression of thiC is significantly higher in biofilm as compared to cells in planktonic growth. Based on these results, we propose that Rhizobium sp. IRBG74 is thiamine-limited and requires thiamine transport for efficient biofilm formation and plant colonization. Thiamine synthesis in aerobic bacteria such as Rhizobium requires O2 and thus could be inhibited in the microaerobic/anaerobic conditions in biofilms.
more » « less- NSF-PAR ID:
- 10424065
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- FEMS Microbiology Letters
- Volume:
- 370
- ISSN:
- 1574-6968
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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