Bacterial diversity in Arctic marine sediment determined by culture-dependent and-independent approaches

Bacterial diversity in surface sediment from the Arctic Ocean was investigated by culture-dependent and-independent approaches. Conventional culture-dependent techniques revealed 11 strains based on their distinct morphological characteristics on marine Zobell 2216E agar plates. Phylogenetic analysis showed that these isolates belonged to three major lineages of the Bacteria,γ-proteobacteria, Bacteroidetes and Actinobacteria, and that they included 10 genera. Most isolates were psychrotrophic, and NaCl was not necessary for their growth. Furthermore, they exhibited activity of at least one extracellular hydrolytic enzyme at 4＆#176;C and had various abilities to assimilate carbon sources. A total of 67 phylotypes were detected among 142 clones based on the 16S rRNA library of the total community DNA and grouped into nine major lineages of bacteria. Phylotypes afifliated withγ-,δ-andε-proteobacteria accounted for 36.7%, 21.8%and 16.9%of the total clones, respectively. The rest of the clones belonged to Bacteroidetes,α-proteobacteria, Actinobacteria, Fusobacteria, Nitrospirae and an unclassiifed group.

Comparing results of cultured and uncultured biological methods used in biological phosphorus removal

Increasing attention has been paid to phosphate-accumulating organisms （PAOs） for their important role in biological phosphorus removal. In this study, microbial communities of PAOs cultivated under different carbon sources （sewage, glucose, and sodium acetate） were investigated and compared through culture-dependent and culture-independent methods, respectively. The results obtained using denaturing gradient gel electrophoresis （DGGE） of polymerase chain reaction-amplified 16S rDNA fragments revealed that the diversity of bacteria in a sewage-fed reactor （1#） was much higher than in a glucose-fed one （2#） and a sodium acetate-fed one （3#）; there were common PAOs in three reactors fed by different carbon sources. Five strains were separated from three systems by using a phosphaterich medium; they were from common bacteria isolated and three isolates could not be found in DGGE profile at all. Two isolates had good phosphorus removal ability. When the microbial diversity was studied, the molecular biological method was better than the culture-dependent one. When phosphorus removal characteristics were investigated, culture-dependent approach was more effective. Thus a combination of two methods is necessary to have a comprehensive view of PAOs.

Evaluating the flavor and divergent bacterial communities in corn-based zha-chili

Zha-chili is a naturally fermented traditional food from central southern China.Corn-based zha-chili is one of the most popular varieties with a special flavor.To investigate its distinct microbiome,corn-based zha-chili samples were collected and investigated using both high-throughput sequencing and culture-dependent method.Subsequently,E-nose and E-tongue sensors were used to evaluate the overall sensory profile.We found that the bacterial communities present in zha-chili samples from the two regions were significantly different(P<0.05).Companilactobacillus,Lactiplantibacillus,and Corynebacterium were found to be the dominant genera common to samples from both regions.Among these,lactic acid bacteria were the most dominant.Biomarker genera were Ligilactobacillus,Lactobacillus,and Levilactobacillus(Huaihua)and Pantoea,Lactiplantibacillus,and Weissella(Songtao).Using culture-dependent methods,the most dominant genus Companilactobacillus was found to comprise Companilactobacillus alimentarius and Companilactobacillus futsaii.The sensory profile was also characterized.This indicated that zha-chili from the two regions could be discriminated by sourness and aftertaste-B(E-taste),and W1C,W3C,W5C,W1S,W2S,W5S,and W2W(E-nose).Correlation analysis suggested that the dominant genera might not affect the aroma quality of corn-based zha-chili,whereas they were related to taste quality.Levilactobacillus and Ligilactobacillus were positively correlated with the characteristic taste indices and negatively correlated with the off-flavor indices.Another dominant genus,Kocuria was positively correlated with umami and richness(P<0.05).Our results could provide a basis for supporting zha-chili production and help the isolation of appropriate lactic acid bacteria from corn-based zha-chili.

Exploring the region-wise diversity and functions of symbiotic bacteria in the gut system of wood-feeding termite,Coptotermes formosanus,toward the degradation of cellulose,hemicellulose,and organic dyes

The wood-feeding termite Coptotermes formosanus represents a unique and impressive system for lignocellulose degradation.The highly efficient digestion of lignocellulose is achieved through symbiosis with gut symbionts like bacteria.Despite extensive research during the last three decades,diversity of bacterial symbionts residing in individual gut regions of the termite and their associated functions is still lacking.To this end,cellulose,xylan,and dye-decolorization bacteria residing in foregut,midgut,and hindgut regions of C.formosanus were enlisted by using enrichment and culture-dependent molecular methods.A total of 87 bacterial strains were successfully isolated from different gut regions of C.formosanus which belonged to 27 different species of 10 genera,majorly affiliated with Proteobacteria(80%)and Firmicutes(18.3%).Among the gut regions,37.9%of the total bacterial isolates were observed in the hindgut that demonstrated predominance of cellulolytic bacteria(47.6%).The majority of the xylanolytic and dye-decolorization bacteria(50%)were obtained from the foregut and midgut,respectively.Actinobacteria represented by Dietza sp.was observed in the hindgut only.Based on species richness,the highest diversity was observed in midgut and hindgut regions each of which harbored seven unique bacterial species.The members of Enterobacter,Klebsiella,and Pseudomonas were common among the gut regions.The lignocellulolytic activities of the selected potential bacteria signpost their assistance to the host for lignocellulose digestion.The overall results indicate that C.formosanus harbors diverse communities of lignocellulolytic bacteria in different regions of the gut system.These observations will significantly advance our understanding of the termite–bacteria symbiosis and their microbial ecology uniquely existed in different gut regions of C.formosanus,which may further shed a light on its potential values at termite-modeled biotechnology.