Porphyrobacter neustonensis gen. nov., sp. nov., an Aerobic Bacteriochlorophyll-Synthesizing Budding Bacterium from Fresh Water

Abstract

Four strains of orange-or red-pigmented bacteria isolated from freshwater surfaces were shown to synthesize bacteriochlorophyll under aerobic conditions. These strains shared unusual morphological features, such as acellular stalks, crateriformlike structures, and buds, with bacteria in the order Plunctomycetules. However, comparisons of 16s rRNA sequences showed them to be members of the (11-4 subdivision of the class Proteobucteriu and most closely related to the marine aerobic bacteriochlorophyll-synthesizing bacterium Erythrobacter longus. They also differ from members of the Plunctomycetules phenotypically in their synthesis of bacteriochlorophyll and possession of a peptidoglycan cell wall. They can be distinguished from E. longus on the basis of their 16s rRNA sequence, the G+C content of their DNA, cellular fatty acid composition, and carbon substrate spectrum. A new genus, Porphyrobucter, with a single species, P. neustonensis gen. nov., sp. nov., is proposed for these strains. The type strain is ACM 2844.Classical anoxygenic photosynthetic bacteria typically exhibit repression of bacteriochlorophyll synthesis under aerobic conditions. Strains of several bacterial genera have however been shown to synthesize bacteriochlorophyll under aerobic conditions. Such bacteria include Erythrobacter longus (12, 41), "Erythrobacter sibericus" (61), Roseobacter litoralis and Roseobacter denitrificans (formerly Elythrobacter strain OCh 114) (40), Methylobacterium species (34), Rhodospirillum centenum (60), mutants of Rhodobacter sphaeroides (19,44), and the stem-nodulating Rhizobium strain BTAi 1 (6). The hot-spring mat bacterium Heliothk oregonensis may also synthesize bacteriochlorophyll aerobically under in situ conditions in nature, although this bacterium has not been grown in pure culture (29,30). Microorganisms of this physiological type have been referred to as the aerobic photosynthetic bacteria, with exclusion of the cyanobacteria being understood (39). Some are capable of photophosphorylation and may even possess photosynthetic reaction centers, although they appear not to be phototrophic (10,24,26,38,42,52).We have isolated bacteria capable of synthesizing bacteriochlorophyll under aerobic conditions from fresh water. These bacteria thus bear superficial resemblance to Erythrobacter species including the marine E. longus and the freshwater "E. sibericus." However, our freshwater strains also share some morphological and ultrastructural features with a distinctive group of budding bacteria distant from the class Proteobacteria, the planctomycetes. They display budding reproduction in a similar manner to that seen in the planctomycetes, produce some form of noncellular multifibrillar stalk or fascicle, and possess negative stain-collecting pits in the cell surface, termed crateriform structures, thought to be specific to planctomycetes (36). The phylogenetic possibility thus arose that these bacteria might be related to a quite distinct phylum of eubacteria distant from the Proteobacteria and furthermore on...

Proposal of Sphingomonadaceae Fam. Nov., Consisting of Sphingomonas Yabuuchi et al. 1990, Erythrobacter Shiba and Shimidu 1982, Erythromicrobium Yurkov et al. 1994, Porphyrobacter Fuerst et al. 1993, Zymomonas Kluyver and van Niel 1936, and Sandaracinobacter Yurkov et al. 1997, with the Type Genus Sphingomonas Yabuuchi et al. 1990

“…We confirmed that the GC contents of the DNA of the type strains of the species in the alpha-4 group ranged from 58.2 to 66 mol% GC from literature (1,7,8,10,17,18,21,25,26,33,34,(36)(37)(38).…”

“…The 14 new species are: S. macrogoltabidus Takeuchi et al 1993'; S. sanguis Takeuchi et al 1993' and S. terrae Takeuchi et al 1993' (25); 3-ketolactoseproducing S. rosa Takeuchi et al 1995; S. pruni Takeuchi et al 1995; S. asaccharolytica Takeuchi et al 1995" and S. mali Takeuchi et al 1995" (26); S. chlorophenolica Nohynek et al 1995' (17); S. herbicidovorans Zipper et al 1996' (38); S. subarctica Nohynek et al 1996 (18); S. trueperi Kaempfer et al 1997' (10); an aromatic-degrading species, S. aromaticivorans Balkwill et al 1997 proposed for a strain isolated from a marine cyanobacterial mat (36). A new genus, Porphyrobacter Fuerst et al 1993, with a single type species, P. neustonensis Fuerst et al 1993', was proposed for aerobic bacteriochlorophyll-synthesizing bacteria (7). Another species, P. tepidarius, was proposed by Hanada et al 1997 (8).…”

The Phylogenetic Position of the Family Methylococcaceae

“…Genomic DNA was obtained from cells by freezing and thawing; centrifugation was used to remove cell debris. In vitro amplification of 16s ribosomal DNA genes and subsequent sequencing of the amplicon were performed as described by Fuerst et al (7). The regions of the 16s ribosomal DNA sequences that could be aligned unambiguously (also referred to as the eubacterial mask) as described by Lane (8) were aligned; each sequence included 1,298 nucleotides.…”

The mixotrophic nature of photosynthetic plants

“…This process is probably not involved in mixotrophy in anoxygenic photosynthetic bacteria, since the planctomycetes have a uniquely complex cell structure for a bacterium, and no planctomycete is known to have photosynthesis (Fuerst et al 1993). However, a planctomycete contains proteorhodopsin (McCarren and DeLong 2007), so the endocytosis-like means of protein uptake could be involved in this variant on mixotrophy.…”