| Pyropia haitanensis, distributed in the intertidal zone of coastal marine area, is the unique species of China. Its tolerance mechanism of specific environmental stress makes itself the model species for the study of the red algae, which has important value of ecological and scientific researches. In recent years, the scale of cultivation of seaweed farming continues to grow, meanwhile, several of diseases threatens its healthy production. In this paper, a strain of Cobetia sp.X1 is isolated from the P.haitanensis with green rot disease, based on the identification and pathogenicity studies, the X1 was identified as a new species → Cobetia pyropiae sp.nov.. The whole genome sequencing of X1 is completed, which provides the basic data for P. haitanensis epidemiology and disease control.1. Identification and pathogenicity study of green rot disease pathogen:This study investigated the green rot disease that attacks Pyropia haitanensis, an economically important red alga that is extensively farmed in Sourthern China.An dominant bacterium was isolated and was able to cause the same characteristic histopathology as that in natural infections. The bacterial isolate was gram-negative, short rod,0.6～1 μm×0.4μm. It was identified as a member of the genus Cobetia by 16SrRNA gene sequence analysis. After 7 days of infection with 104-108cfu/ml XI, the P. haitanensis blades exhibited 13.8～100% diseased spot area rates. The higher the concentration of infection, the faster the disease progression.2. Identification of Cobetia pyropiae sp.nov.:This isolate grew well at temperatures from 4 ℃to 37 ℃. salinities from 5% to 20% and pH from 6 to 10. The optimum growth condition was 32 ℃,10% salinity and pH 7.5-8.5. X1 is negative to gelatinases, amylase, casein enzyme. Tween 40 and Tween 80, but Tween 20 reaction is positive. X1 is positive to aGLU, βGAL, aGAL and LIP, susceptible to 18 antibiotics. Contains the main fatty acids of the X1 are C 16:1 w7c/16:1 w6c(32.92%), C 16:0(19.18). C12:03-OH(16.04%). C18:1 w7c/18:1 w6c(9.83%), C 12:0(8.18%), C!7:0cyclo(7.86%).These characteristics have obvious differences with other Cobetia bacteria.According to the 16SrRNA, X1 and C. marina are more closer, by predicting DNA-DNA hybridization with C. marina results is 61.10%+/-2.83, between 50%-70%, so the X1 can be identified as a new species, named Cobetia pyropiae sp. nov..3. Whole genome sequencing of C. pyropiae sp.nov. X1 strains:Whole genome sequencing of X1 strains is carried out, according to the genetic information. The number of cells for test is 3, genome size is 3.88M, get 100% of the data and a complete circular genome mapping. Genome total C+G content is 62.35%, the number of predicted and annotations CDS with 3,431 and the average length of CDS with 986 bp, with 7 16s-23s-5s rRNA and 72 tRNA, and by COG and KEGG database statistics and VFDB analysis showed that most of the genes annotated in the glucose and lipid transport and metabolism, amino acid transport and metabolism, nucleic acids and enzymes; 8% of CDS are responsible for the relevant virulence factor genes, including flagella, filus, extracellular polysaccharides, transport systems and secretion systems et al. |
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