Metagenomic analysis further extends the role of Chloroflexi in fundamental biogeochemical cycles.

Chloroflexi members are ubiquitous and have been extensively studied; however, the evolution and metabolic pathways of Chloroflexi members have long been debated. In the present study, the evolution and the metabolic potentials of 17 newly obtained Chloroflexi metagenome-assembled genomes (MAGs) were evaluated using genome and horizontal gene transfer (HGT) analysis. Taxonomic analysis suggests that the MAGs of the present study might be novel. One MAG encodes genes for anoxygenic phototrophy. The HGT analysis suggest that genes responsible for anoxygenic phototrophy in the MAG might have been transferred from Proteobacteria/Chlorobi. The evolution of anaerobic photosynthesis, which has long been questioned, has now been shown to be the result of HGT events. An incomplete Wood-Ljungdahl pathway (with missing genes metF, acsE, fdh, and acsA) was reported in Dehalococcoidetes members. In the present study, MAGs that were not the Dehalococcoidetes members encode genes acsA, acsB, metF and acsE. The genes responsible for sulfate reduction (sat, cysC and sir), dissimilatory sulfite reductase (dsrA and dsrB), and aerobic and anaerobic carbon monoxide oxidation (coxSML and cooSF) were detected in the present study MAGs. The present study expands our knowledge of the possible metabolic potentials of the phylum Chloroflexi and clarifies the evolution of anaerobic photosynthesis.

Halophilic archaea and their extracellular polymeric compounds in the treatment of high salt wastewater containing phenol.

Phenol is one of the major organic pollutants in high salt industrial wastewaters. The biological treatment of such waste using microorganisms is considered to be a cost-effective and eco-friendly method. However, in this process, salt tolerance of microorganisms is one of the main limiting factors. Halophilic microorganisms, especially halophilic archaea are thought to be appropriate for such treatment. To develop a novel effective biological method for high salt phenol wastewater treatment, the influence of phenol in high salt phenol wastewater on halophilic archaea and their extracellular polymeric substances (EPS) should be investigated. In the present study, using phenol enrichment method, 75 halophilic archaeal strains were isolated from Wuyongbulake salt lake sediment sample. The majority of the identified strains were phenol-tolerant. Six strains with high phenol tolerance were chosen, and the phenol scavenging effect was observed in the microbial suspension, supernatant, and EPS. It was noticed that the phenol degradation rate of suspensions of both strains 869-1, and 121-1 in salt water exhibited the highest rates of 83.7%, while the supernatant of strain 869-1 reached the highest rate of 78.2%. When combined with the comprehensive analysis of the artificial wastewater simulation experiment, it was discovered that in the artificial wastewater containing phenol, the phenol degradation rate of suspension of strain A387 exhibited the highest rates of 55.74% both, and supernatant of strain 630-3 reached the highest rate of 62.3%. The EPS produced by strains A00135, 558-1, 869-1, 121-1 and A387 removed 100% phenol within 96 h, and the phenol removal efficiency of EPS produced by 869-1 reached 56.1% under an artificial wastewater simulation experiment with high salt (15%NaCl) condition. The present study suggests that halophilic archaea and their EPS play an important role in phenol degradation. This approach could be potentially used for industrial high-salt wastewater treatment.

Haloterrigena gelatinilytica sp. nov., a new extremely halophilic archaeon isolated from salt-lake.

Two extremely halophilic strains, designated SYSU A558-1T and SYSU A121-1, were isolated from a saline sediment sample collected from Aiding salt-lake, China. Cells of strains SYSU A558-1T and SYSU A121-1 were Gram-stain-negative, coccoid, and non-motile. The strains were aerobic and grew at NaCl concentration of 10-30% (optimum, 20-22%), at 20-55 °C (optimum, 37-42 °C) and at pH 6.5-8.5 (optimum, 7.0-8.0). Cells lysed in distilled water. The polar lipids were phosphatidyl choline, phosphatidylglycerol phosphate methyl ester, disulfated diglycosyl diether-1 and unidentified glycolipid. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the two strains SYSU A558-1T and SYSU A121-1 were closely related to the membranes of the genus Haloterrigena. Phylogenetic and phylogenomic trees of strains SYSU A558-1T and SYSU A121-1 demonstrated a robust clade with Haloterrigena turkmenica, Haloterrigena salifodinae and Haloterrigena salina. The genomic DNA G + C content of strains SYSU A558-1T and SYSU A121-1 were 65.8 and 65.0%, respectively. Phenotypic, phylogenetic, chemotaxonomic and genome analysis suggested that the two strains SYSU A558-1T and SYSU A121-1 represent a novel species of the genus Haloterrigena, for which the name Haloterrigena gelatinilytica sp. nov. is proposed. The type strain is SYSU A558-1T (= KCTC 4259T = CGMCC 1.15953T).

Halegenticoccus tardaugens sp. nov., an extremely halophilic archaeon isolated from a saline soil.

Two extremely halophilic archaea, isolates SYSU A00711T and SYSU A00630, were isolated from a sediment soil sample collected from the Aiding lake, China. Cells of these isolates were cocci, non-motile and stained Gram-negative. They grew optimally at 37 °C, with 20-22% NaCl (w/v) and at pH 7.5-8.0. Cells lysed in distilled water. Major polar lipids were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, mannosyl glucosyl diether, sulfated mannosyl glucosyl diether, and two unidentified glycolipids. Pairwise sequence comparison revealed that isolates SYSU A00711T and SYSU A00630 were closely related to Halegenticoccus soli SYSU A9-0T (94.1 and 94.0% 16S rRNA gene sequence similarities; 94.0 and 94.2% rpoB' gene similarities, respectively). The overall genomic relatedness indices values between the two isolates and Halegenticocus soli SYSU A9-0 T were: AAI, both 79.6%; ANI, 84.6 and 84.5%; dDDH, 32.5 and 26.3%, respectively. Phylogenetic trees based on the 16S rRNA gene, rpoB' gene, and genome sequences demonstrated a robust clade of these two isolates with Halegenticoccus soli SYSU A9-0T. The DNA G + C contents of these two isolates are both 64.7% (genome method). Based on the differences in phenotypic, chemotaxonomic, and phylogenetic properties, isolates SYSU A00711T and SYSU A00630 are characterized to represent a novel species in the genus Halegenticoccus, for which the name Halegenticoccus tardaugens sp. nov. is proposed. The type strain of the species Halegenticoccus tardaugens is SYSU A00711T (= KCTC 4245T = CGMCC 1.15768T).

Transcriptomic responses of haloalkalitolerant bacterium Egicoccus halophilus EGI 80432T to highly alkaline stress.

The haloalkalitolerant bacterium Egicoccus halophilus EGI 80432T exhibits high adaptability to saline-alkaline environment. The salinity adaptation mechanism of E. halophilus EGI 80432T was fully understood based on transcriptome analyses and physiological responses; however, the alkaline response mechanism has not yet been investigated. Here, we investigated the alkaline response mechanism of E. halophilus EGI 80432T by a transcriptomic comparison. In this study, the genes involved in the glycolysis, TCA cycle, starch, and trehalose metabolism for energy production and storage, were up-regulated under highly alkaline condition. Furthermore, genes responsible for the production of acidic and neutral metabolites, i.e., acetate, pyruvate, formate, glutamate, threonine, and ectoine, showed increased expression under highly alkaline condition, compared with the control pH condition. In contrast, the opposite results were observed in proton capture or retention gene expression profiles, i.e., cation/proton antiporters and ATP synthases. The above results revealed that E. halophilus EGI 80432T likely tended to adopt an "acidic metabolites production" strategy in response to a highly alkaline condition. These findings would pave the way for further studies in the saline-alkaline adaptation mechanisms of E. halophilus EGI 80432T, and hopefully provide a new insight into the foundational theory and application in ecological restoration with saline-alkaline strains.

Gulosibacter sediminis sp. nov., isolated from Indian Ocean marine sediment.

A novel Gram-stain-positive, catalase-positive, oxidase-negative, aerobic, non-motile, rod-shaped bacterium, designated strain YIM M12148T, was isolated from a marine sediment sample collected from the Indian Ocean. The strain grew optimally at 28 °C, pH 8.0 and in the presence of 1-3 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM M12148T belongs to the genus Gulosibacter, with the highest sequence similarity to Gulosibacter faecalis NBRC 15706T (96.12 %). The cell-wall sugars of strain YIM M12148T were rhamnose, ribose, glucose and mannose. The predominant isoprenoid quinones were MK-8 and MK-9. The polar lipids consisted of major amounts of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unknown phospholipid and one unknown lipid. Major fatty acids (>5 % of the total) of the novel isolate were anteiso-C15 : 0, iso-C15 : 0, iso-C13 : 0 and anteiso-C13 : 0. The genomic DNA G+C content of strain YIM M12148T was 67.15 mol%. On the basis of genotypic and phenotypic data, it is apparent that strain YIM M12148T represents a novel species of the genus Gulosibacter, for which the name Gulosibacter sediminis sp. nov. is proposed. The type strain is YIM M12148T (=KCTC 29660T=DSM 29154T).

Physicochemical and Microbial Diversity Analyses of Indian Hot Springs.

In the present study, physicochemical and microbial diversity analyses of seven Indian hot springs were performed. The temperature at the sample sites ranged from 32 to 67°C, and pH remained neutral to slightly alkaline. pH and temperature influenced microbial diversity. Culture-independent microbial diversity analysis suggested bacteria as the dominant group (99.3%) when compared with the archaeal group (0.7%). Alpha diversity analysis showed that microbial richness decreased with the increase of temperature, and beta diversity analysis showed clustering based on location. A total of 131 strains (divided into 12 genera and four phyla) were isolated from the hot spring samples. Incubation temperatures of 37 and 45°C and T5 medium were more suitable for bacterial isolation. Some of the isolated strains shared low 16S rRNA gene sequence similarity, suggesting that they may be novel bacterial candidates. Some strains produced thermostable enzymes. Dominant microbial communities were found to be different depending on the culture-dependent and culture-independent methods. Such differences could be attributed to the fact that most microbes in the studied samples were not cultivable under laboratory conditions. Culture-dependent and culture-independent microbial diversities suggest that these springs not only harbor novel microbial candidates but also produce thermostable enzymes, and hence, appropriate methods should be developed to isolate the uncultivated microbial taxa.

Correction to: Description of Paenibacillus yunnanensis sp. nov., Isolated from a Tepid Spring.

It was brought to our attention that the proposed name Paenibacillus yunnanensis is an illegitimate homonym of Paenibacillus yunnanensis Niu et al. 2015. We therefore propose changing the name of the newly proposed species to Paenibacillus tengchongensis as follows.

Description of Paenibacillus yunnanensis sp. nov., Isolated from a Tepid Spring.

A Gram stain-positive, rod-shaped and motile bacterium, designated SYSU G01003T was isolated from a sediment sample collected from tepid spring in Tengchong, Yunnan province, southwestern China. Growth observed at temperature ranging 28-37 °C (optimum 37 °C) and pH 6.0-8.0 (optimum pH 7.0). Tolerance to NaCl was up to 2.5% (w/v) (optimal in the absence of NaCl). The cell wall peptidoglycan is meso-2,6-diaminopimelic acid and MK-7 as the only respiratory quinone. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and unidentified aminophospholipid, phospholipid, and polar lipid. The major fatty acids are C16:0, anteiso-C15:0 and C14:0. The genomic DNA G + C content of the type strain was 54.0 mol%. The average nucleotide identity (ANIb and ANIm) values between SYSU G01003T and Paenibacillus azotifigens LMG 29963T were below the cut-off level (95-96%) recommended as the average nucleotide identity (ANI) criterion for interspecies identity. Based on the above results strain SYSU G01003T represents a novel species of the genus Paenibacillus, for which the name Paenibacillus yunnanensis sp. nov. is proposed. The type strain, SYSU G01003T (=KCTC 43132T = CGMCC 1.17384T).

Genomic Insights of "Candidatus Nitrosocaldaceae" Based on Nine New Metagenome-Assembled Genomes, Including "Candidatus Nitrosothermus" Gen Nov. and Two New Species of "Candidatus Nitrosocaldus".

"Candidatus Nitrosocaldaceae" are globally distributed in neutral or slightly alkaline hot springs and geothermally heated soils. Despite their essential role in the nitrogen cycle in high-temperature ecosystems, they remain poorly understood because they have never been isolated in pure culture, and very few genomes are available. In the present study, a metagenomics approach was employed to obtain "Ca. Nitrosocaldaceae" metagenomic-assembled genomes (MAGs) from hot spring samples collected from India and China. Phylogenomic analysis placed these MAGs within "Ca. Nitrosocaldaceae." Average nucleotide identity and average amino acid identity analysis suggested the new MAGs represent two novel species of "Candidatus Nitrosocaldus" and a novel genus, herein proposed as "Candidatus Nitrosothermus." Key genes responsible for chemolithotrophic ammonia oxidation and a thaumarchaeal 3HP/4HB cycle were detected in all MAGs. Furthermore, genes coding for urea degradation were only present in "Ca. Nitrosocaldus," while biosynthesis of the vitamins, biotin, cobalamin, and riboflavin were detected in almost all MAGs. Comparison of "Ca. Nitrosocaldales/Nitrosocaldaceae" with other AOA revealed 526 specific orthogroups. This included genes related to thermal adaptation (cyclic 2,3-diphosphoglycerate, and S-adenosylmethionine decarboxylase), indicating their importance for life at high temperature. In addition, these MAGs acquired genes from members from archaea (Crenarchaeota) and bacteria (Firmicutes), mainly involved in metabolism and stress responses, which might play a role to allow this group to adapt to thermal habitats.

[Influence of methyl esterification on the ultraviolet absorption of gamma-linolenic acid].

OBJECTIVE: To study the influence of methyl esterification on the ultraviolet absorption of gamma-linolenic acid. METHODS: To measure the ultraviolet absorption value of some gamma-linolenic acid product by Ultraviolet Spectrophotometry before and after methyl esterification and to measure the fatty acids formation with gas chromatographic method. Then to do a correlation analysis of the results. RESULTS: The ultraviolet absorption value of gamma-linolenic acid before methyl esterification was very significantly correlated with that after methyl esterification. CONCLUSION: It is feasible to mesure the ultraviolet absorption value of polyunsaturated fatty acids (such as gamma-linolenic acid) without methyl esterification.