Cultivation of Walsby?s square haloarchaeon

Abstract

The square haloarchaea of Walsby (SHOW group) dominate hypersaline microbial communities but have not been cultured since their discovery 25 years ago. We show that natural water dilution cultures can be used to isolate members of this group and, once in pure culture, they can be grown in standard halobacterial media. Cells display a square morphology and contain gas vesicles and poly-beta-hydroxybutyrate (PHB) granules. The 16S rRNA gene sequence was >99% identical to other SHOW group sequences. They prefer high salinities (23-30%), and can grow with a doubling time of 1-2 days in rich media. The ability to culture SHOW group organisms makes it possible to study, in a comprehensive way, the microbial ecology of salt lakes.

Characterization of heterotrophic prokaryote subgroups in the Sfax coastal solar salterns by combining flow cytometry cell sorting and phylogenetic analysis

“…These two major groups of halobacteriales have been recently found to be dominant in three, geographically distant, Australian crystallizer ponds (Oh et al 2010). These observations agree with the findings that show representatives of the genus Halorubrum and Haloquadratum to be well adapted to extremely high salt concentrations (close or at the saturation point) (Bolhuis et al 2004; Burns et al 2004a, 2007; Papke et al 2007). …”

Comparison of prokaryotic community structure from Mediterranean and Atlantic saltern concentrator ponds by a metagenomic approach

“…Sequences related to Haloquadratum were positively correlated with potassium, magnesium, and sulfate ions while sequences related to Halorubrum , Haloarcula , Halonotius , Halobaculum , and Salinibacter were negatively correlated with them. In addition, H. walsbyi shows a higher tolerance to Mg 2+ than other halophilic archaea (Bolhuis et al, 2004; Burns et al, 2004). The differences found among Isla Cristina and Santa Pola datasets, mainly due to the dominance of sequences related to Halorubrum in IC21 and to Haloquadratum in SS19 and SS33, might be explained by the difference in the ionic composition of both samples as previously reported in other hypersaline habitats (Pagaling et al, 2009; Grant et al, 2011; Boujelben et al, 2012; Podell et al, 2013).…”

Transcriptome analysis of Haloquadratum walsbyi: vanity is but the surface

“…After its initial discovery by Anthony E. Walsby in 1980 [3], the organism could not be cultivated for almost 25 years, until 2004 when two strains were isolated and described and their genomes were sequenced. In addition to the Spanish isolate HBSQ001 [4, 5] and the H. walsbyi type strain, the Australian strain C23 [6, 7], a further 5 strains were isolated (M. Dyall-Smith, personal communication) and two partial genomes were assembled from metagenome datasets [8]. H. walsbyi HBSQ001, is a true halophile that under laboratory conditions grows optimally at a doubling time of about 10 days in near saturated NaCl media (3.3 M) with high concentrations of MgCl 2 (2 M) [4, 6].…”

“…In addition to the Spanish isolate HBSQ001 [4, 5] and the H. walsbyi type strain, the Australian strain C23 [6, 7], a further 5 strains were isolated (M. Dyall-Smith, personal communication) and two partial genomes were assembled from metagenome datasets [8]. H. walsbyi HBSQ001, is a true halophile that under laboratory conditions grows optimally at a doubling time of about 10 days in near saturated NaCl media (3.3 M) with high concentrations of MgCl 2 (2 M) [4, 6]. In natural brines, H. walsbyi succeeds as a K -strategist, species with overall lower energy demands that are capable of efficiently utilizing a vast number of scarce resources [9, 10], in contrast to R -strategists, that are mainly fast-growing organisms adapted for high resource utilization.…”