Characterization of Porphyrobacter sanguineus sp. nov., an aerobic bacteriochlorophyll-containing bacterium capable of degrading biphenyl and dibenzofuran

Abstract

Three strains of "Agrobacterium sanguineum", an aerobic marine bacterial species described previously, were re-characterized from phylogenetic and taxonomic viewpoints. 16S rDNA sequence comparisons showed that the "A. sanguineum" strains belong to the α-4 subgroup of α-Proteobacteria, with members of the genera Erythromicrobium and Porphyrobacter as their closest relatives. DNA-DNA hybridization studies indicated that the "A. sanguineum" strains were distinguishable from any previously known species of these genera. Bacteriochlorophyll a, monosaccharide-type glycosphingolipids, 2-OH fatty acids of C14:0, C15:0, C16:0, and C16:1, and ubiquinone-10 were detected in the "A. sanguineum" strains. The G+C of the DNA was 63.8-64.0 mol%. Two of the "A. sanguineum" strains, IAM 12620 (=ATCC 25659) and ATCC 25661, were able to grow with biphenyl and dibenzofuran as sole carbon source in the presence of 0.05% yeast extract. The medium in these cultures turned yellowish-orange at the exponential phase of growth due to the release of soluble chromogenic metabolites. The remaining "A. sanguineum" strain, ATCC 25660, and all test strains of Erythromicrobium and Porphyrobacter neither grew nor produced yellow-orange pigment with biphenyl or dibenzofuran. In PCR experiments, bphA1 gene, coding for the large subunit protein of biphenyl dioxygenase, was detected in "A. sanguineum" IAM 12620 and ATCC 25661. Based on these results, we propose classifying "A. sanguineum" IAM 12620 and ATCC 25661 as a new species of the genus Porphyrobacter with the name Porphyrobacter sanguineus sp. nov.