Citromicrobium bathyomarinum, a novel aerobic bacterium isolated from deep-sea hydrothermal vent plume waters that contains photosynthetic pigment-protein complexes

Abstract

We have taxonomically and phylogenetically characterized a new aerobic bacterial strain (JF-1) that contains photosynthetic pigment-protein complexes and which was recently isolated from black smoker plume waters of the Juan de Fuca Ridge. Strain JF-1 is a gram-negative, yellow-pigmented, motile bacterium that is salt-, pH-, and thermotolerant. These properties are consistent with an oligotrophic adaptation to varied environmental conditions thought to exist around deep-sea hydrothermal vents. The analysis of 16S rDNA sequences revealed that strain JF-1 forms a separate phylogenetic branch between the genus Erythromonas and the Erythromicrobium-Porphyrobacter-Erythrobacter cluster within the alpha subclass of the Proteobacteria. The taxonomic name Citromicrobium bathyomarinum (gen. nov., sp. nov.) is proposed for strain JF-1.

FIG. 1

Electron micrographs of negatively stained cells. (A) Pleomorphism of cells; (B) flagellation of a single cell; (C and D) cells of different morphologies connected by an unknown material (indicated by arrows); (E and F) enlarged regions of panel D, showing membranous connective material (indicated by arrows) and a bubbly substance. Bars, 2 μm (A), 1 μm (B and D), and 0.5 μm (C, E, and F).

FIG. 2

Different types of cell division revealed in electron micrographs of thin-sectioned cells. (A) Example of cell binary division with peptidoglycan layer and cytoplasmic membrane invagination. The nucleoid is seen as light zones. (B) Asymmetric constriction; (C) interesting type of cell division; (D through F) different stages of Y cell division. The nucleoids are distributed in three directions. Bars, 0.25 μm.

FIG. 3

(A) Absorption spectrum of intact cells showing carotenoid and Bchl peaks. Inset, enlarged 650- to 950-nm region of the spectrum showing the presence of the photosynthetic RC (small peak at 800 nm) and LHI (major peak at 867 nm). (B) Absorption spectrum of sucrose gradient fraction of detergent-solubilized membranes enriched in the LHI-RC complex.

FIG. 4

Strain JF-1 is capable of growth over a broad range of NaCl concentrations, pH values, and temperatures in RO media.

FIG. 5

Dendrogram showing the phylogenetic position of strain JF-1, designated C. bathyomarinum, among members of the genera Sphingomonas, Erythromonas, Erythrobacter, Sandaracinobacter, and Porphyrobacter within the α-subclass of the Proteobacteria. The sequence of A. tumefaciens was used to root the dendrogram. Bootstrap values (expressed as percentages of 500 replications) of 65% or more are indicated at the branch points. Bar, 5% sequence divergence.