Phylogenetic affiliation of the bacteria that constitute phototrophic consortia

Abstract

The phylogenetic affiliation of epibionts occurring in three morphologically distinct types of green-colored phototrophic consortia was investigated. Intact consortia of the types "Chlorochromatium aggregatum", "C. glebulum", and a third previously undescribed type, tentatively named "C. magnum" were mechanically separated from accompanying bacteria by either micromanipulation or by chemotactic accumulation in sulfide-containing capillaries. A 540-base-pair-long fragment of the 16S rRNA gene of the epibionts was amplified employing PCR primers specific for green sulfur bacteria. DNA fragments were separated by denaturing gradient gel electrophoresis and subsequently sequenced. The results of this phylogenetic analysis indicated that the symbiotic epibionts, together with only a few free-living strains, form a cluster within the green sulfur bacterial radiation which is only distantly related to the majority of known representatives of this phylum. Consortia with identical morphology but different origin exhibited significant differences in their partial 16S rRNA gene sequences, which could be confirmed by analysis of the 16S rRNA secondary structure. The phylogenetic affiliation of the chemotrophic central rod-shaped bacterium of "C. aggregatum" and "C. magnum" was analyzed by fluorescent in situ hybridization. According to our results and contrary to earlier assumptions, the central bacterium is a member of the beta-subgroup of the Proteobacteria.

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“…It turned out that the consortium can be enriched with 2-oxoglutarate to which it is chemotactically attracted (Fröstl & Overmann 1998). 16S rRNA probing revealed that the chemotrophic central bacterium in these consortia belongs to the β-proteobacteria and is highly unlikely to reduce sulfur compounds (Fröstl & Overmann 2000). Thus, the concept of a sulfur cycle as basis for this cooperation has to be revised.…”

Single-Cell Microbiology: Tools, Technologies, and Applications

“…Examples include the isolation of cells for subsequent analyses such as single-cell PCR, the selection of cells with unique or beneficial characteristics, and the isolation of cells to obtain pure cultures of microorganisms that are difficult to purify using traditional culture-based methods (5,81,83,124). This can also be extended to include the direct isolation of dormant, stressed, or otherwise unculturable cells for further study (22).…”

“…However, the advent of computer-assisted stage or micromanipulator movement and more sensitive methods for fluid aspiration and deposition has led to improvements in the basic technology. Together, these improvements have resulted in more accurate, more accessible, and less exacting processes for the mechanical manipulation of microbial cells (81,82,83).…”

Building communities one bacterium at a time

“…One might assume that there are many examples of syntrophic interactions among microorganisms because of their diversity and abundance (1,2). Remarkably few cases between 2 or more microbial species have been described, however, and even fewer have been characterized in detail (3)(4)(5)(6). With incomplete evidence to support the mechanisms that are involved in the emergence of symbiosis, a central question remains unanswered: how do different microbes become mutually agreeable neighbors?…”