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BMC Genomics. 2017 Jul 3;18(1):510. doi: 10.1186/s12864-017-3892-2.

Transcriptome analysis of Haloquadratum walsbyi: vanity is but the surface.

Author information

1
Department of Marine Microbiology and Biogeochemistry, Royal Netherlands Institute for Sea Research (NOIZ) and Utrecht University, Den Hoorn, the Netherlands. henk.bolhuis@nioz.nl.
2
Evolutionary Genomics Group, Departamento de Producción Vegetal y Microbiología, Universidad Miguel Hernández, San Juan de Alicante, Alicante, Spain.
3
Faculty of Medicine, University Sarajevo School of Science and Technology, Sarajevo, Bosnia and Herzegovina.

Abstract

BACKGROUND:

Haloquadratum walsbyi dominates saturated thalassic lakes worldwide where they can constitute up to 80-90% of the total prokaryotic community. Despite the abundance of the enigmatic square-flattened cells, only 7 isolates are currently known with 2 genomes fully sequenced and annotated due to difficulties to grow them under laboratory conditions. We have performed a transcriptomic analysis of one of these isolates, the Spanish strain HBSQ001 in order to investigate gene transcription under light and dark conditions.

RESULTS:

Despite a potential advantage for light as additional source of energy, no significant differences were found between light and dark expressed genes. Constitutive high gene expression was observed in genes encoding surface glycoproteins, light mediated proton pumping by bacteriorhodopsin, several nutrient uptake systems, buoyancy and storage of excess carbon. Two low expressed regions of the genome were characterized by a lower codon adaptation index, low GC content and high incidence of hypothetical genes.

CONCLUSIONS:

Under the extant cultivation conditions, the square hyperhalophile devoted most of its transcriptome towards processes maintaining cell integrity and exploiting solar energy. Surface glycoproteins are essential for maintaining the large surface to volume ratio that facilitates light and organic nutrient harvesting whereas constitutive expression of bacteriorhodopsin warrants an immediate source of energy when light becomes available.

KEYWORDS:

Archaea; Bacteriorhodopsin; Glycoprotein; Halophile; Haloquadratum; Transcriptome

PMID:
28673248
PMCID:
PMC5496347
DOI:
10.1186/s12864-017-3892-2
[Indexed for MEDLINE]
Free PMC Article

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