Unusually High Archaeal Diversity in a Crystallizer Pond, Pomorie Salterns, Bulgaria, Revealed by Phylogenetic Analysis

Recent studies on archaeal diversity in few salterns have revealed heterogeneity between sites and unique structures of separate places that hinder drawing of generalized conclusions. Investigations on the archaeal community composition in P18, the biggest crystallizer pond in Pomorie salterns (PS) (34% salinity), demonstrated unusually high number of presented taxa in hypersaline environment. Archaeal clones were grouped in 26 different operational taxonomic units (OTUs) assigned to 15 different genera from two orders, Halobacteriales and Haloferacales. All retrieved sequences were related to culturable halophiles or unculturable clones from saline (mostly hypersaline) niches. New sequences represented 53.9% of archaeal OTUs. Some of them formed separate branches with 90% similarity to the closest neighbor. Present results significantly differed from the previous investigations in regard to the number of presented genera, the domination of some genera not reported before in such extreme niche, and the identification of previously undiscovered 16S rRNA sequences.

ALGAL DISTRIBUTION AND ITS ABUNDANCE IN PUTHALAM SALTWORKS, KANYAKUMARI DISTRICT, TAMIL NADU

Saltworks are important wetlands and exposed to wide range of environmental stress and perturbations. Fluctuations of salinity, brine chemistry and nutrient status leads to variation in microalgal population. The typical saltworks Sri Sankara Allom, Puthalam was chosen for the study. The investigation was aimed to list out the microalgae and calculates their abundance. The work was done in different seasons (I, II, III and IV) of the study period (March 2009 to February 2010). The reservoir pond showed major variation among micro algal species but it was low in condenser pond. Only two micro algal species were observed in crystallizer pond. A gradual reduction in number of micro algal species was observed with an increase in salinity. With regard to crystallizer, Dunaliella was the dominant one throughout the study period.

Natronomonas moolapensis sp. nov., non-alkaliphilic isolates recovered from a solar saltern crystallizer pond, and emended description of the genus Natronomonas

Two isolates of non-alkaliphilic, extremely halophilic archaea, with very similar characteristics, were recovered from a marine solar saltern crystallizer. Cells were pleomorphic, motile and Gram-stain-negative and grew on a limited range of carbon sources, with pyruvate being the best substrate. Optimum growth occurred at 18–20 % (w/v) NaCl, pH 6.0–8.5 and 37–40 °C. Both isolates possessed typical archaeal lipids, and their 16S rRNA gene sequences were 99.8 % identical. Phylogenetic tree reconstructions indicated that they were most closely related to the haloalkaliphile Natronomonas pharaonis (97.5 % similarity to the type strain), but the different phenotypic properties and low DNA–DNA hybridization values between Nmn. pharaonis DSM 2160T and the two isolates suggested that they represent a novel species within the genus Natronomonas. The name Natronomonas moolapensis sp. nov. is proposed for these isolates, with the type strain being 8.8.11T (=JCM 14361T =CECT 7526T =DSM 18674T). An emended description of the genus Natronomonas is also provided.

Abundance and biomass of prokaryotic and eukaryotic microorganisms coupled with environmental factors in an arid multi-pond solar saltern (Sfax, Tunisia)

The distribution of abundance and biomass of prokaryotes, flagellates, ciliates and phytoplankton, were studied in five ponds of increasing salinity in the Sfax solar saltern (Tunisia) coupled with environmental factors. The results showed that abundance of eukaryotic microorganisms decreased with increasing salinity of the ponds whereas prokaryotes (heterotrophic bacteria and Archaea) were abundant in the hyper-saline ponds. Phototrophic picoplankton was found in a large range of salinity values (70 and 200‰). Phototrophic non-flagellated nanoplankton which dominated in the first sampled pond was substituted by phototrophic flagellated nanoplankton in the other ponds. Heterotrophic nanoplankton dominated in the crystallizer pond but its quantitative importance declined in the less saline ponds. Diatoms and dinoflagellates were the major contributors to phytoplankton abundance in the first ponds (>90% of total abundance). Ciliated protozoa were found in all the ponds except in the crystallizer in which prokaryotes proliferated. Oligotrichida and Heterotrichida were the most abundant ciliate groups. Overall, species richness decreased with salinity gradient. We propose a simplified diagram of the Sfax saltern's food web showing the dominant role of the microbial loop along the salinity gradient.

Combined Use of Cultivation-Dependent and Cultivation-Independent Methods Indicates that Members of Most Haloarchaeal Groups in an Australian Crystallizer Pond Are Cultivable

ABSTRACT Haloarchaea are the dominant microbial flora in hypersaline waters with near-saturating salt levels. The haloarchaeal diversity of an Australian saltern crystallizer pond was examined by use of a library of PCR-amplified 16S rRNA genes and by cultivation. High viable counts (106 CFU/ml) were obtained on solid media. Long incubation times (≥8 weeks) appeared to be more important than the medium composition for maximizing viable counts and diversity. Of 66 isolates examined, all belonged to the family Halobacteriaceae, including members related to species of the genera Haloferax, Halorubrum, and Natronomonas. In addition, isolates belonging to a novel group (the ADL group), previously detected only as 16S rRNA genes in an Antarctic hypersaline lake (Deep Lake), were cultivated for the first time. The 16S rRNA gene library identified the following five main groups: Halorubrum groups 1 and 2 (49%), the SHOW (square haloarchaea of Walsby) group (33%), the ADL group (16%), and the Natronomonas group (2%). There were two significant differences between the organisms detected in cultivation and 16S rRNA sequence results. Firstly, Haloferax spp. were frequently isolated on plates (15% of all isolates) but were not detected in the 16S rRNA sequences. Control experiments indicated that a bias against Haloferax sequences in the generation of the 16S rRNA gene library was unlikely, suggesting that Haloferax spp. readily form colonies, even though they were not a dominant group. Secondly, while the 16S rRNA gene library identified the SHOW group as a major component of the microbial community, no isolates of this group were obtained. This inability to culture members of the SHOW group remains an outstanding problem in studying the ecology of hypersaline environments.