Iron and Manganese Homeostasis in Marine Bacteria

Green, Robert (2012) Iron and Manganese Homeostasis in Marine Bacteria. Doctoral thesis, University of East Anglia.

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Using a mixture of bioinformatic analyses, microarrays on cells that were grown in media that were
either replete or depleted for manganese or for iron, and by making targeted mutations and
reporter fusions, several important observations were made on the mechanisms of Mn and Fe
homeostasis in the marine α‐proteobacterium Ruegeria pomeroyi (the main species studied here),
and in other important marine bacteria.
R. pomeroyi lacks most of the known Fe uptake systems, including TonB and outer‐membrane
receptors, but has a predicted, but incomplete iron uptake ABC‐class transporter operon, whose
expression is much enhanced in Fe‐depleted conditions, although a strain lacking these genes was
unaffected in growth. The Fe‐specific regulatory network of R. pomeroyi was found to involve the Irr
transcriptional regulator, which controlled the expression of several genes. Microarrays revealed
many other genes whose expression was enhanced or diminished in Fe‐replete conditions, providing
material for future work on the iron regulon of this bacterium,
Turning to manganese, here too the expression of many genes was affected (up or down) by Mn
availability. These included an operon corresponding to sitABCD, an effective ABC‐type Mn2+
transporter in many other bacteria. This was confirmed, directly, to be the case for Ruegeria.
Bioinformatic analyses showed that some other Roseobacter strains lacked any previously known
Mn2+ transporter, but instead, had a gene that likely encoded an inner membrane protein and was
preceded by a motif (MRS box) that was known to be recognised by the Mn2+ ‐responsive
transcriptional regulator Mur. It was confirmed that this gene, termed mntX, did indeed encode a
manganese transporter and that MntX orthologues occurred in several other, unrelated marine
bacteria, notably most strains of the pathogenic genus Vibrio (including V. cholerae) and some of the
most abundant bacteria in the oceans, namely the SAR11 clade (Pelagibacter).

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Users 2259 not found.
Date Deposited: 06 Mar 2014 12:18
Last Modified: 06 Mar 2014 12:18

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