Cytochromes c and the evolution of Gram positive bacteria

• Main Author: Hreggvidsson, Gudmundur Oli
• Published: University of Edinburgh 1993
• Subjects: 579
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.652651

The content and cellular location of cytochromes in <I>Bacillus azotoformans</I> was examined under aerobic and denitrifying anaerobic conditions. An abundance of cytochromes was expressed. Two cytochromes were induced under aerobic conditions, one of which was only expressed under conditions of high aeration. One cytochrome, a b-type cytochrome, may be induced under denitrifying conditions. Cytochromes common to both pathways appear to be expressed in similar amounts per unit cell weight. Both c- and b-type cytochromes from <I>B. azotoformans</I> appear to be membrane bound, as they were only detected in membrane fractions. Different methods for releasing cytochromes from cell membranes were tried. Only extraction with detergents and mild proteolytic treatment were successful. Four different membrane bound cytochromes from <I>Bacillus azotoformans</I>, designated P1-c552, P2-c551, P3&P4-c555 and P5-c552, were isolated and purified. The bases of classification of Class I cytochromes c are examined and revisions are suggested to the existing classification schemes. The evolutionary implications of the distribution of the proposed cytochrome c groups in the phylogenetic eubacterial tree, based on 16sRNA analyses, are discussed. The past and present ideas about the evolution of the phylum of Gram positive bacteria are presented and discussed in the light of the present sequence information of cytochromes c and other electron transport proteins. The electron transport pathway in the genus <I>Bacillus</I> is compared with its counterparts in distantly related bacteria. The significance of observed similarities and differences, in types of cytochromes and composition, for the elucidation of the evolutionary history of the Gram positive phylum as well as for eubacteria in general, is emphasised.