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Morphological and structural aspects of the extremely halophilic archaeon Haloquadratum walsbyi.

ABSTRACT: Ultrathin square cell Haloquadratum walsbyi from the Archaea domain are the most abundant microorganisms in the hypersaline water of coastal salterns and continental salt lakes. In this work, we explore the cell surface of these microorganisms using amplitude-modulation atomic-force microscopy in nearly physiological conditions. We demonstrate the presence of a regular corrugation with a periodicity of 16-20 nm attributed to the surface layer (S-layer) protein lattice, striped domains asymmetrically distributed on the cell faces and peculiar bulges correlated with the presence of intracellular granules. Besides, subsequent images of cell evolution during the drying process indicate the presence of an external capsule that might correspond to the giant protein halomucin, predicted by the genome but never before observed by other microscopy studies.

SUBMITTER: Sublimi Saponetti M

PROVIDER: S-EPMC3084702 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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Morphological and structural aspects of the extremely halophilic archaeon Haloquadratum walsbyi.

Sublimi Saponetti Matilde M Bobba Fabrizio F Salerno Grazia G Scarfato Alessandro A Corcelli Angela A Cucolo Annamaria A

PloS one 20110429 4

Ultrathin square cell Haloquadratum walsbyi from the Archaea domain are the most abundant microorganisms in the hypersaline water of coastal salterns and continental salt lakes. In this work, we explore the cell surface of these microorganisms using amplitude-modulation atomic-force microscopy in nearly physiological conditions. We demonstrate the presence of a regular corrugation with a periodicity of 16-20 nm attributed to the surface layer (S-layer) protein lattice, striped domains asymmetric ...[more]

PMID: 21559517

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Project description:BackgroundHaloquadratum walsbyi commonly dominates the microbial flora of hypersaline waters. Its cells are extremely fragile squares requiring >14%(w/v) salt for growth, properties that should limit its dispersal and promote geographical isolation and divergence. To assess this, the genome sequences of two isolates recovered from sites at near maximum distance on Earth, were compared.Principal findingsBoth chromosomes are 3.1 MB in size, and 84% of each sequence was highly similar to the other (98.6% identity), comprising the core sequence. ORFs of this shared sequence were completely synteneic (conserved in genomic orientation and order), without inversion or rearrangement. Strain-specific insertions/deletions could be precisely mapped, often allowing the genetic events to be inferred. Many inferred deletions were associated with short direct repeats (4-20 bp). Deletion-coupled insertions are frequent, producing different sequences at identical positions. In cases where the inserted and deleted sequences are homologous, this leads to variant genes in a common synteneic background (as already described by others). Cas/CRISPR systems are present in C23(T) but have been lost in HBSQ001 except for a few spacer remnants. Numerous types of mobile genetic elements occur in both strains, most of which appear to be active, and with some specifically targetting others. Strain C23(T) carries two ∼6 kb plasmids that show similarity to halovirus His1 and to sequences nearby halovirus/plasmid gene clusters commonly found in haloarchaea.ConclusionsDeletion-coupled insertions show that Hqr. walsbyi evolves by uptake and precise integration of foreign DNA, probably originating from close relatives. Change is also driven by mobile genetic elements but these do not by themselves explain the atypically low gene coding density found in this species. The remarkable genome conservation despite the presence of active systems for genome rearrangement implies both an efficient global dispersal system, and a high selective fitness for this species.

Dataset Information

Morphological and structural aspects of the extremely halophilic archaeon Haloquadratum walsbyi.

Publications

Morphological and structural aspects of the extremely halophilic archaeon Haloquadratum walsbyi.

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