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Title:Genetic relatedness of the family Rhodospirillaceae: Genome plasticity, chromosome heterogeneity, and chalcogenic oxyanion reductase activity in Rhodobacter sphaeroides
Author(s):Moore, Mark David
Director of Research:Kaplan, Samuel
Doctoral Committee Chair(s):Maloy, Stanley R.
Department / Program:Microbiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Molecular
Biology, Genetics
Biology, Microbiology
Abstract:Intrinsic high-level resistance (HLR) to tellurite (TeO$\sb3\sp{2-}),$ selenite (SeO$\sb3\sp{2-}),$ and at least fifteen other chalcogenic oxides and oxyanions has been demonstrated in the facultative photoheterotrophic bacterium, Rhodobacter (Rba.) sphaeroides. Detailed analyses have shown that HLR to at least one class of these oxyanions, the "tellurite class" (e.g., $\rm TeO\sb4\sp{2-},\ TeO\sb3\sp{2-},\ SeO\sb4\sp{2-},\ SeO\sb3\sp{2-},$ and $\rm Rh\sb2O\sb3),$ occurred via a metalloid oxyanion reductase (MORase), and resulted in elemental deposition in the cytoplasmic membrane, and concomitant H$\sb2$ evolution during photoheterotrophic growth in the presence of these oxyanions. Based on the analysis of TnphoA-derived mutants, the periplasmic-localized dimethyl sulfoxide/trimethylamine-N-oxide reductase (which has been isolated and purified to homogeneity) is not involved in the reduction of these oxyanions. Examination of other Rba. sphaeroides mutants, however, has determined the obligate requirement for an intact CO$\sb2$ fixation pathway and the presence of a functional photosynthetic electron transport chain to effect HLR to TeO$\sb3\sp{2-}$-class oxyanions under photosynthetic growth, and functional cytochromes $b,\ c\sb1$ and $c\sb2$ to facilitate HLR under aerobic growth conditions.
Other members of the Rhodospirillaceae, including members of the $\alpha$-2 and $\alpha$-3 subgroups, were also shown to effect the reduction of many of these compounds, although genera from the $\alpha$-1, $\beta$-1, and $\gamma$-3 subgroups did not. Fifty strains representing six species of purple non-sulfur bacteria were examined for intrinsic HLR to TeO$\sb3\sp{2-}.$ These species were further characterized by total genomic DNA restriction pattern analysis using low-frequency cleavage restriction endonucleases and transverse alternating-field gel electro-phoresis. Genomic schizotypes were obtained for wild-type strains of Rba. sphaeroides and related Proteobacteria. Analysis of these macrorestriction pattern polymorphisms enabled a rapid differentiation of closely-related strains and permitted an estimation of the minimum genome size of each strain. The genetic relationship of these bacteria has been established using maximum parsimony analyses. Evidence is presented for the existence of considerable genetic diversity and genome plasticity among seemingly similar wild-type strains. It has been demonstrated using readily-identifiable DNA macrorestriction fragments that not all strains currently identified as Rba. sphaeroides contain two chromosomes. Genetic schizotyping of strains contained in international culture depositories revealed that not all Rba. sphaeroides strains currently bearing the type strain designation are identical. Based on these results, a major rearrangement of the genus Rhodobacter is proposed.
Issue Date:1994
Rights Information:Copyright 1994 Moore, Mark David
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9503276
OCLC Identifier:(UMI)AAI9503276

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