Epibacterial Community Structure Of Several Macroalgae

Epiphytic bacteria are abundant and ubiquitous colonizers of the external surfacesof marine macroalgae, but relatively little is known about the nature of theirinteraction or the perceived benefits to the macroalgae. This bacteria are generallyassumed to be essential for the development, defense and morphogenesis of algaes,and some bacteria are opportunistic pathogens of host algae. In order to fully assessand explore such interactions, an improved understanding of the composition anddynamics of the surface community is required. We isolated some bacteria fromseveral macroalge sampled from different sites of China coast and investigated thebacterial community of another seveal macroalge simped in Dalian by16S rDNAclone library analysis.Totally606strains were isloated from the surface of22macroalgae samples(Porphyra yezoensis, P. haitanensis, Gracilaria lemaneiformis, G. tenuistipitata,Eucheuma striatum, Grateloupia filicina, Grateloupia filicina) and identified by aphylogenetic analysis of the16S rDNA sequences. They were composed of4phylum:Proteobacteria (84.48%), Bacteroidetes (7.43%), Firmicutes (7.10%) andActinobacteria (0.99%).Gammaproteobacteria (84.16%of the total,16genera) was apparently amajordivision of Pretobacteria, and a large portion (54.29%of the total) fell withinthe genus Pseudoalteromonas. Other strains of Gammaproteobacteria belonged tothe genera Acinetobacter, Alteromonas, Amphritea, Cobetia, Colwellia, Escherichia,Halomonas, Marinomonas, Photobacterium, Pseudomonas, Psychrobacter,Psychromonas, Shewanella, Stenotrophomonas and Vibrio. Marine Bacteroidetesincluding10genera, Algibacter, Cellulophaga, Maribacter, Olleya, Persicivirga,Polaribacter, Psychroserpens, Tenacibaculum, Winogradskyella, Zobellia, wasanother large group found in the culturable part of epibacterial community.Strains ofthe genera Desemzia, Jeotgalicoccus, Salinicoccus, Staphylococcus in the Firmicutes,Microbacterium, Micrococcus in the Actinobacteria, and Brevundimonas,Pseudoruegeria in the Alphaproteobacteria were also be found.Within different samples of the same algal species, the composition of bacteria wassubjected to shifts at the bacterial genus level. Composition patterns of cultural epibacteria of P. yezoensis differed not only in the types of genera but also in therelative proportions of those tpyes within different sampling sites. This phenomenonre-occurred in P. haitanensis, G. lemaneiformis, G. tenuistipitata but all the samplesof this three algae species had the the same dominant genus, Pseudoalteromonas.Composition pattern of two samples of E. striatum were nearly the same but slightlydiffered in proportions of some genera. Few stains were isolated from surface of G.filicina, and only one genus, Pseudomonas, was found coexisting in the two samples.All the isolates from G. filicina belonged to Pseudoalteromonas.Pseudoalteromonas was the dominant group of all the algal species but P. yezoensis.Vibrio was isolated from surface of all algae species but G. filicina.Pseudomonas andStaphylococcus were also in different five algal species, respectively. Obviousdifferences of other genera appeared between different algal species, and many generawere only isolated from one algal species.Cluster analysis and Non-metric multi-dimensional scaling analysis (NMDS)indicated that the cultured part of the epibacterial community of macroalgae wasdetermined by algal species and sampling regions. In this study, no more similaritywas found on closely related host species.Epibacterial community of another7macroalgae (P. yezoensis, Mazzaella sp.,Gloiopeltis furcata, G. lemaneiformis, Ulva pertusa, Undaria pinnatifida, Laminariajaponica) sampled in Dalian were studied with molecular technical method. The16SrDNA clone libriaries analysis revealed that the epibacterial community weredominated by the Proteobacteria and Bacteroidetes. Bacterial phylotypes associatedwith P. yezoensis were affiliated with the genera Ahrensia, Octadecabacter,Roseobacter, Sulfitobacter, Cocleimonas, Moritella, Psychromonas, Formosa, Olleya,Winogradskyella, and Olleya was the dominant genus, about27.87%of the totalclones. Bacterial phylotypes associated with Mazzaella sp. belonged to the generaLoktanella, Pseudoruegeria, Robiginitomaculum, Roseovarius, Sulfitobacter,Aliivibrio, Colwellia, Leucothrix, Oleispira, Pseudoalteromonas, Psychrobacter,Psychromonas, Polaribacter, and Leucothrix dominated the libriay, about14.81%. Alarge portion (42.37%) of clone libriary associated with Gloiopeltis furcata fall withinthe genus Pseudoalteromonas and the genera Octadecabacter, Roseovarius,Sulfitobacter, Alteromonas, Leucothrix, Marinomonas, Lacinutrix were also be found.Only γ-proteobacteria was found in clone libriary associated with G. lemaneiformis,and the clones belonged to the genera Alteromonas, Colwellia, Oceanisphaera,Photobacterium, Pseudoalteromonas, Psychrobacter, Psychromonas, Vibrio. Pseudoalteromonas dominated the libriary, about67.86%. Bacterial phylotypesassociated with Ulva pertusa were mainly assigned to Altererythrobacter,Bradyrhizobium, Erythrobacter, Octadecabacter, Roseovarius, Sulfitobacter,Psychromonas, Winogradskyella, Bacillus, and Octadecabacter was the donminant28%. Clone libriary associated with Undaria pinnatifida was comprised of the generaLoktanella, Alteromonas, Colwellia, Granulosicoccus, Leucothrix, Moritella,Oceanisphaera, Pseudoalteromonas, Psychrobacter, Psychromonas, Rheinheimera,Bizionia, Lacinutrix, Polaribacter, and Leucothrix was the main part,46%. Clonelibriary associated with Laminaria japonica showed the lowest bacterial diversity.Only three genera were found in the libriary: Pseudoalteromonas, Psychromonas,Vibrio and Pseudoalteromonas was the dominant part,91.67%of the total clones.Comparisons of different clone libraries showed obvious differences between theepibacterial community of different macroalgae. Totally, the7clone libraries contains34genera.18genera were found only in one clone library。Ahrensia, Roseobacter,Cocleimonas, Formosa and Winogradskyella were be found only in the clone libraryof P. yezoensis and Pseudoruegeria, Robiginitomaculum, Aliivibrio, Oleispira inMazzaella sp., and Photobacterium in G. furcata, and Marinomonas in G.lemaneiformis, and Altererythrobacter, Bradyrhizobium, Erythrobacter, Bacillus in U.pertusa, and Granulosicoccus, Rheinheimera, Bizionia in U. pinnatifida. Theremained genera existed in several clone libraries. Psychromonas existed in6clonelibraries, not founded in clone library of G. lemaneiformis. Pseudoalteromonas wasthe domintant in epibacterial community of G. lemaneiformis and Gloiopeltis furcata,and Leucothrix in Mazzaella sp., U. pinnatifida. Clone library of P. yezoensis, U.pertusa, L. japonica was dominant with Olleya, Octadecabacter, Psychromonasrespectively.Cluster analysis of clone libraries showed that the variability between thecommunity of different algal species was generally high.2D-NMDS analysis alsoindicated that obvious but slightly differences existed between different phylum ofalgae.