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Mutualistic interactions between vitamin B12 -dependent algae and heterotrophic bacteria exhibit regulation

Kazamia, Elena, Czesnick, Hjördis, Nguyen, Thi Thanh Van, Croft, Martin T., Sherwood, Emma, Sasso, Severin, Hodson, Sarah James, Warren, Martin J., Smith, Alison G. (2012) Mutualistic interactions between vitamin B12 -dependent algae and heterotrophic bacteria exhibit regulation. Environmental Microbiology, 14 (6). pp. 1466-1476. ISSN 1462-2912. (doi:10.1111/j.1462-2920.2012.02733.x) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:34196)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided.
Official URL:
http://dx.doi.org/10.1111/j.1462-2920.2012.02733.x

Abstract

Many algae are auxotrophs for vitamin B(12) (cobalamin), which they need as a cofactor for B(12) -dependent methionine synthase (METH). Because only prokaryotes can synthesize the cobalamin, they must be the ultimate source of the vitamin. In the laboratory, a direct interaction between algae and heterotrophic bacteria has been shown, with bacteria supplying cobalamin in exchange for fixed carbon. Here we establish a system to study this interaction at the molecular level. In a culture of a B(12) -dependent green alga Chlamydomonas nivalis, we found a contaminating bacterium, identified by 16S rRNA analysis as Mesorhizobium sp. Using the sequenced strain of M.?loti (MAFF303099), we found that it was able to support the growth of B(12) -dependent Lobomonas rostrata, another green alga, in return for fixed carbon. The two organisms form a stable equilibrium in terms of population numbers, which is maintained over many generations in semi-continuous culture, indicating a degree of regulation. However, addition of either vitamin B(12) or a carbon source for the bacteria perturbs the equilibrium, demonstrating that the symbiosis is mutualistic and facultative. Chlamydomonas reinhardtii does not require B(12) for growth because it encodes a B(12) -independent methionine synthase, METE, the gene for which is suppressed by addition of exogenous B(12) . Co-culturing C.?reinhardtii with M.?loti also results in reduction of METE expression, demonstrating that the bacterium can deliver the vitamin to this B(12) -independent alga. We discuss the implications of this for the widespread distribution of cobalamin auxotrophy in the algal kingdom.

Item Type: Article
DOI/Identification number: 10.1111/j.1462-2920.2012.02733.x
Subjects: Q Science
Divisions: Divisions > Division of Natural Sciences > Biosciences
Depositing User: Lin Riches
Date Deposited: 06 Jun 2013 14:53 UTC
Last Modified: 16 Nov 2021 10:11 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/34196 (The current URI for this page, for reference purposes)

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