Distinguishing features of δ-proteobacterial genomes

We analyzed several features of five currently available delta-proteobacterial genomes, including two aerobic bacteria exhibiting predatory behavior and three anaerobic sulfate-reducing bacteria. The 5 genomes are distinguished from other bacteria by several properties: (i) The 5 genomes contain two giant S1 ribosomal protein genes in contrast to all other bacterial types, which encode a single or no S1; (it) in most 5-proteobacterial genomes the major ribosomal protein (RP) gene cluster is near the replication terminus whereas most bacterial genomes place the major RP cluster near the origin of replication; (iii) the 8 genomes possess the rare combination of discriminating asparaginyl and glutaminyl tRNA synthetase (AARS) together with the amidotransferase complex (Gat CAB) genes that modify Asp-tRNAAsn into Asn-tRNA(Asn) and GIu-tRNA(Gln) into Gln-tRNA(Gln); (iv) the TonB receptors and ferric siderophore receptors that facilitate uptake and removal of complex metals are common among 5 genomes; (v) the anaerobic 5 genomes encode multiple copies of the anaerobic detoxification protein rubrerythrin that can neutralize hydrogen peroxide; and (Vi) 0,54 activators play a more important role in the 5 genomes than in other bacteria. 6 genomes have a plethora of enhancer binding proteins that respond to environmental and intracellular cues, often as part of two-component systems; (vii) 5 genomes encode multiple copies of metallo-beta-lactamase enzymes; (viii) a host of secretion proteins emphasizing SecA, SecB, and SecY may be especially useful in the predatory activities of Myxococcus xanthus; (ix) delta proteobacteria drive many multiprotein machines in their periplasms and outer membrane, including chaperone-feeding machines, jets for slime secretion, and type IV pili. Bdellovibrio replicates in the periplasm of prey cells. The sulfate-reducing 8 proteobacteria metabolize hydrogen and generate a proton gradient by electron transport. The predicted highly expressed genes from 5 genomes reflect their different ecologies, metabolic strategies, and adaptations.