Phylogenetic diversity of bacterial biofilms covering the settlement substrates of nona-porous abalones(Haliotis diversicolor supertexta)

The settlement substrates of nona-porous abalones (Haliotis diversicolor supertexta) are covered with biofilms in which several types of microorganisms coexist and interact.These microorganisms are usually important causes of juvenile abalone disease as well as organisms useful in promoting abalones' adhesion.The bacterial community structure of the biofilms remains unclear.The aim of this research was to determine the genetic diversity and phylogenetic affiliation of the biofilm bacteria.Total DNA of bacteria in biofilms was extracted,and 16S rRNA gene clone library was constructed using the primers specific for the domain bacteria.Subsequently,30 randomly selected positive clones were screened by PCR-restriction fragment length polymorphism (PCR-RFLP) analysis,and resulted in 15 different RFLP patterns.Sequences analysis of representatives from each unique RFLP type revealed high genetic diversity in the bacterial populations.These sequences fell into nine major lineages of the bacterial domains:α-,β-,γ- and δ-subdivisions of the Proteobacteria; Planctomycete,Actinobacteria,Firmicutes,Verrucomicrobium spp.,and CytophagaFlexibacter-Bacteroides spp.Phylogenetic analysis indicated that the dominant phylotypes were most closely related to environmental and clinical Burkholderia cepacia of the β-Proteobacteria,and Roseobacteria of the α-Proteobacteria.