| Chitinimonas sp R3-44 was a bacterium that has photoinduced lethal effect and produce yellow-green pigments isolated from Arctic soil.Its non-pigment-producing white mutant strain R-7 was much less sensitive to light than the wild-type strain R3-44 produced yellow-green pigments,but the photosensitivity was increased after the addition of the yellow-green pigments extracted from the strain R3-44.Therefore,speculated that yellow-green pigments is a key factor for the sensitivity of strain R3-44to light.In this paper,the composition,characteristics and possible genes of strain R3-44 pigments were studied.It was found that the yellow-green pigments of strain R3-44 consists of three pigment components of orange,yellow and blue,and was sensitive to light.It becomes colorles at alkaline pH,and returns to yellow-green at neutral and acidic pH.Fluorescence was generated by excitation at 365 nm,380 nm,400 nm,and 470 nm.Aryl polyene(APE)-like pigment gene cluster was found in the genome of strain R3-44,and it was found by transcriptome analysis that five genes f3127,f3130,f3133,f3136 and f3143 were involved in the synthesis of pigments.Combining gene prediction,transcriptome analysis,pigment characteristics,and HPLC pigment purification peak maps,it is speculated that yellow pigment may contain a new class of APE pigments.When studying the effect of light intensity on the strain,it was found that the strain R3-44 had photochromism under low dose blue light(50 J/cm2)irradiation.Under anaerobic or micro-aerobic conditions,the yellow-green color of the cells turns Reddish brown,and under aerobic conditions,the yellow-green color turns blue-green,and the reddish brown color changes to blue-green immediately after the oxygen was introduced.The blue-green pigment involved in this phenomenon and its mechanism were studied:it was found that blue-green pigment has a unique absorption peak at 592nm and 642 nm;its formation is not related to live bacteria,but it requires precursor substances in the cells.Produced after combining with yellow-green pigment irradiated by low-dose blue light.This unknown precursor is not sensitive to heat,proteases,or nucleases.It is speculated that reddish brown pigments is formed before the formation of blue-green pigments,and then oxidized to blue-green pigment;in this process,it may have anti-oxidation effect and improve the survival rate of the strain under low-dose blue light irradiation.In summary,the study laid the foundation for further exploring the light-sensitive properties of strain R3-44 and revealing this special life phenomenon.The antarctic is a very special environment with geographical and climatic conditions.There is high radiation,low rainfall,rare vegetation,perennial snow,freezing,low temperature,extreme enthalpy or extreme night have caused the special living environment of microorganisms.This provides a good condition for the analysis of microbial diversity,the excavation of functional strains and the separation of related specific microorganisms.In this context,313 strains were isolated from S0-4,S1-4,S2-4,S3-4,S4-4,and S5-4 samples collected from the terraces of the Antarctic Fildes Peninsula.They were belonging to Proteobacteria(50%),Actinobacteria(27%)and Bacteroidetes(23%)and were affiliated to 23 genera.Two potential new taxa were found and subsequently,polyphasic taxonomic analysis were studied.In the polyphasic taxonomic studies of strain YZ-8T,isolated from a soil sample taken from the fildes peninsula,antarctic,was found to be a Gram-stain-negative,yellow-pigmented,oxidase-and catalase-positive,non-motile,non-spore-forming,rod-shaped and aerobic bacterium.Strain YZ-8T grew optimally at pH 7.0 and 20C.Tolerance to NaCl was up to 0.3%(w/v)with optimum growth in the absence of NaCl.Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YZ-8T belonged to the family Sphingomonas.Strain YZ-8T showed the highest sequence similarities with Sphingomonas molluscorum KMM 3882T(94.40%).The predominant respiratory isoprenoid quinone and polyamine components were identified as ubiquinone Q-10 and sym-homospermidine,respectively.In addition,carotenoid were also found.The polar lipid profile of the strain YZ-8T was found to contain one phosphatidylethanolamine,an unidentified phospholipid,one diphosphatidylglycerol,one phosphatidylglycerol,two sphingophosphonolipids and two unidentified alkali-stable lipids and one phosphatidylcholine.The G+C content of the genomic DNA was determined to be 58.80 mol%.The genome size of 3,994,557 bp(about 4.0M)contains 3 contigs,of which scf7180000000012(gene ID number)has a loop size of 3.0 M;the other two contigs and plasmid library have relatively high coverage,which may be two plasmids.In addition,the strain YZ-8T predicted a total of 4,370genes,of which 3,364 protein-coding genes.The main fatty acids were summed feature 8(comprising C18:1?7c and/or C18:1?6c,35.40%),summed feature 3(comprising C16:1?7c and/or C16:1?6c,32.60%)and C14:0 2-OH(7.70%).On the basis of the evidence presented in this study,a novel species of the genus Sphingomonas,Sphingomonas paeninsulae sp.nov.,is proposed,with the type strain YZ-8T(=CCTCC AB 2017137T=LMG 31027T).A taxonomic study of a Gram-stain-negative,rod-shaped,motile,non-spore-forming cells,pink-red colony,catalase-and oxidase-positive bacterium,sh-6T,isolated from a contaminated R2A plate in the laboratory was performed.Its optimum growth temperature was 28C and absence of NaCl on R2A plate.Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain sh-6T belongs to the genus Hymenobacter,showing high sequence similarity to Hymenobacter deserti ZLB-3T(95.26%).The predominant respiratory isoprenoid quinone and polyamine components were identified as MK-7 and sym-homospermidine,respectively.The major fatty acids were identified as iso-C15:0,summed feature 4(iso-C17:1 I/anteiso B),iso-C16:0,iso-C17:0 3-OH and iso-C17:0 as the major cellular fatty acids.The polar lipids were identified as phosphatidylethanolamine,five unidentified aminolipids and an unidentified polar lipid.The DNA G+C content of this novel isolate was determined to be 60.5 mol%.The genome size of 4,188,814 bp(about 4.2 M)contains 4 contigs,of which scf7180000000008(gene ID number)has a loop size of 4.1 M;the other 3 contigs and plasmid library have relatively high coverage,which may be plasmid;A total of 3,618 genes were predicted for strain sh-6T,of which 3,520 were protein-coding genes.On the basis of the evidence presented in this study,a novel species of the genus Hymenobacter,Hymenobacter oligotrophus sp.nov.,is proposed,with the type strain sh-6T(=CCTCC AB 2016064T=KCTC 62345T). |
PDF Full Text Request