Microbiology

Summary To date, six candidate genera of anaerobic ammonium‐oxidizing (anammox) bacteria have been identified, and numerous studies have been conducted to understand their ecophysiology. In this study, we examined the physiological characteristics of an anammox bacterium in the genus ‘ C andidatus   J ettenia’. Planctomycete KSU ‐1 was found to be a mesophilic (20–42.5°C) and neutrophilic ( pH 6.5–8.5) bacterium with a maximum growth rate of 0.0020 h −1 . Planctomycete KSU ‐1 cells showed typical physiological and structural features of anammox bacteria; i.e. 29 N 2 gas production by coupling of 15 NH 4 + and 14 NO 2 − , accumulation of hydrazine with the consumption of hydroxylamine and the presence of anammoxosome. In addition, the cells were capable of respiratory ammonification with oxidation of acetate. Notably, the cells contained menaquinone‐7 as a dominant respiratory quinone. Proteomic analysis was performed to examine underlying core metabolisms, and high expressions of hydrazine synthase, hydrazine dehydrogenase, hydroxylamine dehydrogenase, nitrite/nitrate oxidoreductase and carbon monoxide dehydrogenase/acetyl‐ CoA synthase were detected. These proteins require iron or copper as a metal cofactor, and both were dominant in planctomycete KSU ‐1 cells. On the basis of these experimental results, we proposed the name ‘ C a . J ettenia caeni’ sp. nov. for the bacterial clade of the planctomycete KSU ‐1.

A novel anoxygenic photoheterotrophic member of the phylum Acidobacteria , Chloracidobacterium thermophilum strain B sp. nov., was isolated from a cyanobacterial enrichment culture derived from microbial mats associated with Octopus Spring, Yellowstone National Park, WY. C. thermophilum sp. nov. was a Gram-stain-negative rod (diameter, approximately 0.8–1.0 µm; variable length, approximately 2.5 µm), which formed greenish-brown liquid suspension cultures. It was a moderately thermophilic microaerophile and grew in a defined medium at 51 °C (Topt; range 44 to 58 °C) and in the pH range 5.5 to 9.5 (pHopt = ~7.0). The DNA G+C content was 61.3 mol%, and phylogenetic analysis, based on the 16S rRNA sequence, showed that C. thermophilum sp. nov. belongs to subdivision 4 ( Acidobacteriaceae ) of the Acidobacteria . C. thermophilum sp. nov. was unable to synthesize branched-chain amino acids, l-lysine, and vitamin B12, which were required for growth. Although the organism lacked genes/enzymes for autotrophic carbon fixation, bicarbonate was required. Growth was stimulated by other amino acids and 2-oxoglutarate. Cells produced chlorosomes containing a diverse mixture of bacteriochlorophyll (BChl) c derivatives, and additionally, synthesized BChl a P, Chl a PD, and Zn-BChl a′P, which occurred in type-1 homodimeric reaction centres. The carotenoids included echinenone, canthaxanthin, lycopene, γ-carotene and β-carotene. C. thermophilum sp. nov. produced iso-diabolic acid as its major fatty acid and synthesized three hopanoids (diploptene, bacteriohopanetetrol and bacteriohopanetetrol cyclitol ether). Based upon its phenotypic and genotypic properties, the name Chloracidobacterium thermophilum gen. nov., sp. nov. is proposed for this isolate; the type strain is C. thermophilum strain BT (ATCC BAA-2647 = JCM 30199).