Phylogenomic analysis of Anabaenopsis elenkinii (Nostocales, Cyanobacteria).

The saline-alkaline lakes (soda lakes) are the habitat of the haloalkaliphilic cyanobacterium Anabaenopsis elenkinii, the type species of this genus. To obtain robust phylogeny of this type species, we have generated whole-genome sequencing of the bloom-forming Anabaenopsis elenkinii strain CCIBt3563 isolated from a Brazilian soda lake. This strain presents the typical morphology of A. elenkinii with short and curved trichomes with apical heterocytes established after separation of paired intercalary heterocytes and also regarding to cell dimensions. Its genome size is 4 495 068 bp, with a G+C content of 41.98 %, a total of 3932 potential protein coding genes and four 16S rRNA genes. Phylogenomic tree inferred by RAxML based on the alignment of 120 conserved proteins using GTDB-Tk grouped A. elenkinii CCIBt3563 together with other genera of the family Aphanizomenonaceae. However, the only previous available genome of Anabaenopsis circularis NIES-21 was distantly positioned within a clade of Desikacharya strains, a genus from the family Nostocaceae. Furthermore, average nucleotide identity values from 86-98 % were obtained among NIES-21 and Desikacharya genomes, while this value was 76.04 % between NIES-21 and the CCIBt3563 genome. These findings were also corroborated by the phylogenetic tree of 16S rRNA gene sequences, which also showed a strongly supported subcluster of A. elenkinii strains from Brazilian, Mexican and Kenyan soda lakes. This study presents the phylogenomics and genome-scale analyses of an Anabaenopsis elenkinii strain, improving molecular basis for demarcation of this species and framework for the classification of cyanobacteria based on the polyphasic approach.

Bacillus natronophilus sp. nov., an alkaliphilic bacterium isolated from a soda lake.

An alkaliphilic, moderately halophilic, heterotrophic, rod-shaped, spore-forming bacterium (M30T) was isolated from a sediment sample collected from a soda lake (Lake Magadi, Tanzania). Strain M30T was strictly aerobic, catalase-positive, oxidase-negative and non-motile. Growth occurred at 12-43 °C (optimum, 25-30 °C), at pH 8.0-12 (optimum, pH 9.5-10) and at salinities of 0.5-15 % (w/v) NaCl (optimum 5 %). It utilized various sugars and organic acids as sole carbon sources and was positive for amylase, cellulase, gelatinase, protease and xylanase activities. The cell-wall peptidoglycan contained meso-diaminopimelic acid and the polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified lipid and one unidentified phospholipid. The DNA G+C content was 48.9 mol%. The predominant menaquinone was MK-7 and the major fatty acids (>10 %) comprised anteiso-C15 : 0, iso-C15 : 0, and anteiso-C17 : 0. Phylogenetic analysis based on 16S rRNA gene sequence affiliated M30T to the genus Bacillus and showed the highest similarities to Bacillus populi FJAT-45347T (96.4 %) and Bacillus aurantiacus K1-5T (96.2 %). Based on the data from the current polyphasic study, M30T represents a novel species of the genus Bacillus, for which the name Bacillus natronophilus sp. nov. is proposed. The type strain is M30T (=JCM 32118T=CGMCC 1.16739T=MCC 3010T).

Nesterenkonia natronophila sp. nov., an alkaliphilic actinobacterium isolated from a soda lake, and emended description of the genus Nesterenkonia.

A Gram-stain-positive, alkaliphilic, moderately halophilic, cocci-shaped actinobacterium (strain M8T) was isolated from a sample of soda lake sediment (Lake Magadi, Tanzania). The isolate was heterotrophic, strictly aerobic, catalase-positive, oxidase-negative and formed orange-pigmented colonies in solid media. It utilized various sugars and organic acids as sole carbon sources. The organism grew at 10-38 °C, at pH 7.5-12.0 and in the presence of 1-12 % (w/v) NaCl, with optimal growth occurring at 30 °C, at pH 10 and in the presence of 5 % (w/v) NaCl. Comparative 16S rRNA gene sequence analysis showed that strain M8T belonged to the genus Nesterenkonia, sharing the closest similarities to Nesterenkoniahalobia DSM 20541T, Nesterenkoniahalophila YIM 70179T and Nesterenkoniaaethiopica DSM 17733T (97.5, 97.5 and 97.1 %, respectively). The characteristic diamino acid of strain M8T was found to be lysine and the polar lipids detected were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, two unidentified glycolipids and two unidentified phospholipids. The DNA G+C content was 61.8 mol% (genome). The strain contained MK-7, MK-9 and MK-10 as the respiratory quinones, and the major fatty acids (>10 %) comprised anteiso-C17 : 0 and anteiso-C15 : 0. On the basis of phylogenetic analyses and phenotypic data, strain M8T is considered to represent a novel species, for which the name Nesterenkonianatronophila sp. nov. is proposed. The type strain is M8T (=JCM 32100T=CGMCC 1.16706T=MCC 3367T).

Isolation and characterization of novel potent Cr(VI) reducing alkaliphilic amphibacillus sp. ksuCr3 from hypersaline soda lakes

A strain KSUCr3 with extremely high Cr(VI)-reducing ability under alkaline conditions was isolated from hypersaline soda lakes and identified as Amphibacillus sp. on the basis of 16S rRNA gene sequence analysis. The results showed that Amphibacillus sp. strain KSUCr3 was tolerance to very high Cr(VI) concentration (75 mM) in addition to high tolerance to other heavy metals including Ni2+ (100 mM), Mo2+ (75 mM), Co2+ (5 mM), Mn2+ (100 mM), Zn2+ (2 mM), Cu2+ (2 mM) and Pb (75 mM). Strain KSUCr3 was shown to be of a high efficiency in detoxifying chromate, as it could rapidly reduce 5 mM of Cr(VI) to a non detectable level over 24 hrs. In addition, strain KSUCr3 could reduce Cr(VI) efficiently over a wide range of initial Cr(VI) concentrations (1-10 mM) in alkaline medium under aerobic conditions without significant effect on the bacterial growth. Addition of glucose, NaCl and Na2CO3 to the culture medium caused a dramatic increase in Cr(VI)-reduction by Amphibacillus sp. strain KSUCr3. The maximum chromate removal was exhibited in alkaline medium containing 1.5 percent Na2CO3, 0.8 percent glucose, and 1.2 percent NaCl, at incubation temperature of 40ºC and shaking of 100 rpm. Under optimum Cr(VI) reduction conditions, Cr(VI) reduction rate reached 237 uMh¹ which is one of the highest Cr(VI) reduction rate, under alkaline conditions and high salt concentration, compared to other microorganisms that has been reported so far. Furthermore, the presence of other metals, such as Ni2+, Co2+, Cu2+ and Mn2+ slightly stimulated Cr(VI)-reduction ability by the strain KSUCr3.The isolate, Amphibacillus sp. strain KSUCr3, exhibited an ability to repeatedly reduce hexavalent chromium without any amendment of nutrients, suggesting its potential application in continuous bioremediation of Cr(VI). The results also revealed the possible isolation of potent heavy metals resistant bacteria from extreme environment such as hypersaline soda lakes.