Genomics And Transcriptomics Studies Of Chlamydophila Acidophila In Acid Mine Drainage

Acid mine drainage?AMD?is produced by oxidation of sulfide minerals when exposed to the surface for a long time.It is characterized by low pH and high metal content.Microorganisms play a catalytic role in AMD formation,however,compared with prokaryotes,research on eukaryotes is relatively low.Photosynthetic algae are primary producers of many acidic environments and can be used as a carbon source of sulfate-reducing bacteria to AMD remediation.Therefore,they play an indispensable role in the acidic ecological environment.In order to understand the metabolic function and adaptive mechanism of acidophilic algae in an extremely acidic environment,a strain of Chlamydomonas acidophilia was isolated and analyzed by genomics and transcriptomics.The results are as follows:?1?A photosynthetic alga,Chlamydomonas sp.1710,was isolated and purified from pyrite AMD lake in Anhui Province.It was identified as Chlamydomonas acidophilus by 18S rRNA gene sequencing and phylogenetic analysis.The optimum growth conditions were pH of 3.0,the temperature of 10-20oC,and light intensity of180?m E m^-2 s^-1.?2?In the signal transduction pathway of Chlamydomonas sp.1710,heat shock protein?HSP?is synthesized to resist heavy metals.The alga stimulates the synthesis of plant chelating peptides?PCs?by producing glutathione?GSH?to resist high concentrations of metal toxicity.There are abundant fatty acid desaturase?ADS3?,Aldo/keto reductase family protein?AKR4C9?and cationic transport ATPase?HMA4?and DNA repair protein?UVH1?coding genes in the algae genome.The high expression of these genes can help Chlamydomonas sp.1710 adapt to extreme acidic environments.?3?Chlamydomonas sp.1710 was highly tolerant of metals and grew faster in the medium containing 500 mg/L Al than in the control medium.Transcriptomic analysis showed that the alga could efficiently express 3-phosphate glyceraldehyde dehydrogenase?GAPB?and Aldol/keto reductase family proteins?AKR4C9?in 500mg/L Al to eliminate the damage of Al to the cells.?4?Under the 500 mg/L Al culture conditions,the expression of V-type proton ATPase?VHA?was higher than that of the control group.Cationic transporter ATPase?HMA4?,ATPase-coupled ion transmembrane transporter?PAA1?and active ion transmembrane transporter?AHA2?only appeared in 500 mg/L group and are capable of binding heavy metal ions.These metal-resistant genes were expressed due to the increase of Al.?5?In complex V of the oxidative phosphorylation pathway,more metal-binding proteins were detected in the 500 mg/L group than in the control group.Among them,F-type H⁺-ATP transporter alpha subunit and gamma subunit?ATP5A;ATP5C1?and V-type H⁺-ATP transporter subunit B?ATP6B?could respond to heavy metal stress.In photosynthesis,ATP-producing F-type H⁺-ATP synthase subunits A and C?ATPF0A;ATPF0C?were expressed only at 500 mg/L.In addition,glutamine synthase?GLN1-3?,which can help cells cope with heavy metal stress,was also expressed only in 500mg/L samples in glyoxylic acid and dicarboxylic acid metabolism.