The Distribution Of Tetraether Membrane Lipid Produced By Haloalkaliphiles And The Application Of Three Haloalkaliphilic Bacteria

Haloalkaliphiles are a kind of dualextremophilic bacteria thriving under the combined harsh conditions of hypersalinity and extreme alkalinity with the optimum growth salinity greater than 0.5 mol·L–1 and the optimum growth p H higher than 9.0.They are widely used in various fields of human life.With the rapid development of genome sequencing technology,it is possible to obtain the genome DNA sequences of strains with low cost,high efficiency and accuracy,so that we can have a deeper understanding of the genetic basis of haloalkaliphiles and their adaptation mechanism in extreme environments.High performance liquid chromatography–mass spectrometry(HPLC–MS)was used to analyze b GDGTs,and illumina Miseq,dd PCR technology to determine the bacterial community structure of saline-alkali soil samples in Songnen Plain.LC–MS showed that the absolute contents of with fewer cyclopentyl rings b GDGTs were high and could accumulate in soil for a long time.The distribution and relative abundance of b GDGTs were controlled by six environmental variables,and the most powerful environmental factor was p H.High p H limited the number of cyclopentyl rings in b GDGTs.While cyclization index CBT of b GDGTs was negatively correlated with Na+ concentration from 99.83 to 196.72 mg/kg Na+ concentration.The number of 16 S r RNA gene copies in bacteria is the same as that of b GDGTs,which is also affected by p H and Na+.Finally,network analysis showed that the bacterial sources of b GDGT IIa were Catelliglobosispora,Longispora,Truepera,unidentified,Tepidamorphus,Rubricoccus,Planctomyces and Singulisphaera,while the b GDGT IIb was from Pseudomonas.Through the above analysis,the distribution characteristics of b GDGTs and their corresponding relationship with environmental factors were found.The community structure and ecological functions of bacteria were analyzed,and the biological sources of b GDGTs were identified.Illumina sequencing was used to determine the genomic draft of two bacteria isolated from a salinealkali lake in Xinjiang.The aerobic halophilic bacterium Halomonas urumqiensis BZ-SZ-XJ27T growed optimally at 1.42 M.Its draft genome consists of approximately 3.97 Mb and contains 3,588 predicted genes.Some genes maintaining intracellular osmotic balance were identified,such as glycine betaine synthesis,glutamine synthesis and ectoine synthesis genes cluster.Another haloalkaliphilic bacterium Bacillus urumqiensis BZ-SZ-XJ18T,optimum growth occurred at the total Na+ concentration of 1.08 M with a broad optimum of p H 8.5–9.5.The draft genome consists of approximately 3.28 Mb and contains 3,228 predicted genes,including glycine betaine synthesis gene cluster,Trk gene and sodium hydrogen pump gene,which associated with osmotic balance and p H homeostasis.The illumina sequencing provided pertinently insight into specific adaptations to the double extreme environment.The complete genome of xylan degradation bacterium Alkalitalea saponilacus SC/BZ-SP2 T was performed with pac Bio sequencing platform.The genome contained one chromosome with a total size of 4,775,573 bps,and a G+C genomic content of 39.27%.Twelve genes relating to the pathway for complete xylan degradation and various genes involved in osmotic balance and p H homeostasis were systematically identified.GC analysis showed that the main product of xylan fermented by A.saponilacus was propionic acid.Dinitrosalicylic acid(DNS)method was used to determine xylanase activity and 0.4%(w/v)sucrose + 0.1%(w/v)birch xylan was the best carbon source.At the same time,the optimum conditions for extracting crude enzymes were determined and their enzymatic properties were analyzed.The above studies show that propionic acid,the main product of A.saponilacus fermentation,and the biosynthetic thermostable xylanase had broad application prospects in industrial production.