•Proteome of Tetragenococcus halophilus under hypo- and hyper-osmotic stress conditions was studied.•178 proteins accumulated differently under hypo-osmotic stress condition.•131 proteins accumulated differently under hyper-osmotic stress condition.•Tetragenococcus halophilus may overcome osmotic stresses by regulating various cellular life processes.•Post-transcriptional regulation might exist.Tetragenococcus halophilus is a moderate halophilic bacterium which was widely used in fermentation processes, growing in a broad range of salinity conditions, and can survive a saturated 26.47% w/w NaCl concentration. However, the mechanism of this outstanding ability to acclimate to extracellular osmotic stress still remains unknown. The current study firstly conducted a quantitative proteomic analysis to identify alterations of the cellular proteome under both hypo-osmotic and hyper-osmotic stress conditions. A total of 1405 proteins were identified and differentially accumulated proteins were analyzed, further functional annotations were performed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. The results revealed that both hypo- and hyper-osmotic stresses have prominent impacts on the synthesis of proteins involving in multiple cellular functions. Further analyses of the differentially accumulated proteins suggested that the adaptation strategies T. halophilus applies to deal with hypo- and hyper-osmotic stress conditions may be distinct. Comparison of the differentially accumulated proteins in both transcriptomic and proteomic study indicated the existence of post-transcriptional modification during salinity adaptation of T. halophilus. The current study generated a proteomic atlas of differentially accumulated proteins under both hypo- and hyper-osmotic stress conditions, provided an overview of the molecular mechanism of osmotic acclimation of T. halophilus.SignificanceThe current study aimed to reveal how the moderately halophilic Tetragenococcus halophilus adapt to extracellular salinity stress, which is the first proteomic study analyzing the differences in proteome of Tetragenococcus halophilus between hypo- and hyper-osmotic stress to our knowledge. By analyzing the differences in the accumulating levels of the proteome via isobaric labeling-based quantitative proteomic study, we identified proteins with significantly different accumulation levels which may play important roles in the adaptation process to extracellular salinity stress. Examining the cellular functions of these proteins according to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, a draft view of how the bacterium act to acclimate to osmotic stress has been drawn. Further analysis revealing the differences between the transcriptome and proteome suggested that some proteins may undergo post-transcriptional regulation during acclimation process, which still remains unstudied and needs further investigations. The results of the current study can help researchers to gain insights and further reveal the halophilic mechanism of halophiles.Download high-res image (179KB)Download full-size image

Activated sludge is essential for the biological wastewater treatment process and the identification of active microbes enlarges awareness of their ecological functions in this system. Microbial communities and their active members were investigated in activated sludge from a leather sewage treatment plant by a combined approach targeting both 16S rRNA and 16S rRNA genes. Although active bacteria obtained by RNA analysis exhibit similar diversity with DNA-based populations, the distribution of microbes significantly differed between the total and active communities. Several active taxa showed low abundance or even absence in the DNA-derived community. Moreover, microbial consortia, particularly bacterial communities, distinctly distributed at a particular treatment stage and both the total and active bacterial communities displayed high environmental sensitivity. Distributions of archaeal communities remained stable and the overrepresentations of active Cenarchaeaceae and Nitrosopumilaceae were potentially associated with ammonia oxidation across the treatment process. Furthermore, bacteria quantitatively dominate the microbial community in activated sludge and the 16S rRNA : 16S rRNA gene ratios of bacteria were positively correlated with the removal of contaminants. The results indicate that both dominant and low-abundance taxa with high potential activity play pivotal roles in removal of contaminants within sewage.

Paenibacillus aceti L14T (CGMCC 1.15420 = JCM 31170) is a novel species isolated from the solid-state acetic acid fermentation culture of traditional Chinese vinegar. The strain is able to biosynthesize the pyrazines, including 2,3-diisobutylpyrazine, 2-isobutyl-3-methylpyrazine and 1-(5-isobutyl-2-pyrazinyl)-1-propanone. Genome sequencing of L14 was performed to gain insights into the genetic elements involved in the biosynthesis of pyrazines. The genome of L14 contains 5,611,962 bp with a GC content of 47.92 mol%, 5147 protein coding genes, 92 tRNAs, 20 rRNAs and four sRNAs. The strain L14 also contains complete biosynthetic pathways of valine, leucine and isoleucine, and contains genes for encoding threonine dehydratase and ketol-acid reductoisomerase. This genome sequence provides a basis for elucidating the possible mechanism for the biosynthesis of pyrazines.

•Total and active microbes were investigated in activated sludge.•Proteobacteria was the most abundant and active phylum.•Psychrobacter had the highest potential for activity in the anaerobic tank.•16S rRNA: rRNA gene ratios of bacteria and archaea decreased with treatment.Microbes within activated sludge and their potentially metabolic activity are important factors in contaminants removal during actual wastewater treatment. In this study, microbial community structures and metabolic activity in an anaerobic-anoxic-oxic (A2O) system treating soy sauce-producing wastewater were studied using 16S rDNA and rRNA high-throughput sequencing. At DNA and RNA level, microbial communities harbored distinct biodiversity. Proteobacteria was the most abundant and active phylum in activated sludge. Abundant Megasphaera, Thauera and Azoarcus were in slow metabolism, while Psychrobacter with low abundance had the highest potential for activity in the anaerobic tank. As for archaea, Cenarchaeales was the most abundant and active order and a large amount of hydrogenotrophic methanogens kept syntrophic with Megasphaera. The rare taxa, such as Methanosarcinales and Nitrosopumilales, had a high potential for activity in the anoxic tank. Furthermore, the total and active microbes were quantified via DNA and RNA-based qPCR and the 16S rRNA: rRNA gene ratios of bacteria and archaea decreased along with the treatment process. Altogether, the findings provided novel insights into the evolution of microbial activity in an integrated soy sauce-producing wastewater treatment process.

Qishan vinegar is a typical Chinese fermented cereal product that is prepared using traditional solid-state fermentation (SSF) techniques. The final qualities of the vinegar produced are closely related to the multiple bacteria present during SSF. In the present study, the dynamics of microbial communities and their abundance in Daqu and vinegar Pei were investigated by the combination of high throughput sequencing and quantitative PCR. Results showed that the Enterobacteriales members accounted for 94.7%, 94.6%, and 92.2% of total bacterial sequences in Daqu Q3, Q5, and Q10, respectively. Conversely, Lactobacillales and Rhodospirillales dominated during the acetic acid fermentation (AAF) stage, corresponding to the quantitative PCR results. Lactobacillus, Acetobacter, Weissella, Leuconostoc and Bacillus were the dominant and characteristic bacterial genera of Qishan vinegar during AAF process. Redundancy analysis suggested that Lactobacillales and Rhodospirillales had a positive correlation with humidity and acidity, respectively. These results confirmed that the bacterial community structure could be affected by physiochemical factors, which determined the unique bacterial composition at different fermentation stages and showed batch-to-batch consistency and stability. Therefore, the conformity of bacterial community succession with physiochemical parameters guaranteed the final quality of Qishan vinegar products. This study provided a scientific perspective for the uniformity and stability of Qishan vinegar, and might aid in controlling the manufacturing process.

Mushrooms are popular folk medicines that have attracted considerable attention because of their efficient antitumor activities. This review covers existing research achievements on the mechanisms of isolated mushroom polysaccharides, particularly (1→3)-β-D-glucans. Our review also describes the function in modulating the immune system and potential tumor-inhibitory effects of polysaccharides. The antitumor mechanisms of mushroom polysaccharides are mediated by stimulated T cells or other immune cells. These polysaccharides are able to trigger various cellular responses, such as the expression of cytokines and nitric oxide. Most polysaccharides could bind other conjugate molecules, such as polypeptides and proteins, whose conjugation always possess strong antitumor activities. The purpose of this review is to summarize available information, and to reflect the present situation of polysaccharide research filed with a view for future direction.

Solid-state acetic acid fermentation (AAF), a natural or semi-controlled fermentation process driven by reproducible microbial communities, is an important technique to produce traditional Chinese cereal vinegars. Highly complex microbial communities and metabolites are involved in traditional Chinese solid-state AAF, but the association between microbiota and metabolites during this process are still poorly understood. In this study, we performed amplicon 16S rRNA gene sequencing on the Illumina MiSeq platform, PCR-denaturing gradient gel electrophoresis, and metabolite analysis to trace the bacterial dynamics and metabolite changes under AAF process. A succession of bacterial assemblages was observed during the AAF process. Lactobacillales dominated all the stages. However, Acetobacter species in Rhodospirillales were considerably accelerated during AAF until the end of fermentation. Quantitative PCR results indicated that the biomass of total bacteria showed a “system microbe self-domestication” process in the first 3 days, and then peaked at the seventh day before gradually decreasing until the end of AAF. Moreover, a total of 88 metabolites, including 8 organic acids, 16 free amino acids, and 66 aroma compounds were detected during AAF. Principal component analysis and cluster analyses revealed the high correlation between the dynamics of bacterial community and metabolites.

Vinegar is one of the oldest acetic acid-diluted solution products in the world. It is produced from any fermentable sugary substrate by various fermentation methods. The final vinegar products possess unique functions, which are endowed with many kinds of compounds formed in the fermentation process. The quality of vinegar is determined by many factors, especially by the raw materials and microbial diversity involved in vinegar fermentation. Given that metabolic products from the fermenting strains are directly related to the quality of the final products of vinegar, the microbial diversity and features of the dominant strains involved in different fermentation stages should be analyzed to improve the strains and stabilize fermentation. Moreover, although numerous microbiological studies have been conducted to examine the process of vinegar fermentation, knowledge about microbial diversity and their roles involved in fermentation is still fragmentary and not systematic enough. Therefore, in this review, the dominant microorganism species involved in the stages of alcoholic fermentation and acetic acid fermentation of dissimilar vinegars were summarized. We also summarized various physicochemical properties and crucial compounds in disparate types of vinegar. Furthermore, the merits and drawbacks of vital fermentation methods were generalized. Finally, we described in detail the relationships among microbial diversity, raw materials, fermentation methods, physicochemical properties, compounds, functionality, and final quality of vinegar. The integration of this information can provide us a detailed map about the microbial diversity and function involved in vinegar fermentation.

Tetragenococcus halophilus, a moderately halophilic Gram-positive bacterium, was isolated from Chinese style soy sauce. This species is a valuable resource for investigating salt tolerance mechanisms and improving salinity resistance in microorganisms. RNA-seq was used to sequence T. halophilus samples treated with 0 M (T1), 1 M (T2), and 3.5 M NaCl (T3). Comparative transcriptomic analyses of the different treatments were performed using gene ontology and Kyoto encyclopedia of genes and genome. The comparison of T1 and T2 by RNA-seq revealed that genes involved in transcription, translation, membrane system, and division were highly up-regulated under optimum salt condition. The comparison of T2 and T3 showed that genes related to heat shock proteins or the ATP-binding cassette transport systems were significantly up-regulated under maximum-salt condition. In addition, a considerable proportion of the significantly differently expressed genes identified in this study are novel. These data provide a crucial resource that may determine specific responses to salt stress in T. halophilus.

A complementary DNA (cDNA) of nitrate reductase (NR) from Dunaliella bardawil was isolated using RT-PCR and RACEs techniques. The full-length D. bardawil NR (DbNR) cDNA is 3,107 bp containing a putative open reading frame of 2,670 bp in length which encodes 889 amino acids with a calculated molecular weight (MW) of 98.37 kDa, a 34-bp 5′-untranslated region, and a 3′-untranslated region of 403 bp with a poly (A) tail. BLAST search showed that the nucleotide and putative protein sequence exhibit sequence identities of 92 and 79 % with the corresponding gene from Dunaliella tertiolecta, respectively. Protein structural analysis showed a typical NR structure of DbNR with five structural distinctive domains which form three common subparts of eukaryotic NR (Euk-NR). Phylogenetic analysis based on the holo-DbNR and sulfite oxidase (SO) and cytochrome b reductase (CbR) subparts manifested that (1) DbNR has a closer relationship with those counterparts from algae and higher plants than from other species and (2) DbNR might have evolved from ancient SO and CbR in a “domain shuffling” pattern. The glycerol contents and transcriptional expression patterns of DbNR under salt stress and dilution shock treatments were also traced. The results implied an indirect role of NaCl on the induction of DbNR through an osmoregulation pathway.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a well-known proverbial protein involved in various functions in vivo. The functional diversity of GAPDH from Dunaliella bardawil (DbGAPDH) may relate to the regulatory elements lying in the promoter at the transcriptional level. Using RT-PCR and RACE reactions, gapdh cDNA was isolated, and the full-length genomic sequence was obtained by LA-PCR-based genome walking. The full-length cDNA sequence was 1645 bp containing an 1128 bp putative open reading frame (ORF), which coded a 375 amino acids-deduced polypeptide whose molecular weight was 40.27 kDa computationally. Protein conserved domain search and structural computation found that DbGAPDH consists of two structural conserved domains highly homologous in most species; multiple sequence alignment discovered two positive charge residues (Lys164 and Arg 233), which play a critical role in the protein–protein interaction between GAPDH, phosphoribulokinase (PRK), and CP12. Phylogenetic analysis demonstrated that DbGAPDH has a closer relationship with analogues from algae and higher plants than with those from other species. In silico analysis of the promoter region revealed six potential regulatory elements might be involved in four hypothesized functions characterized by chloroplast GAPDH: oxygen-, light-, pathogen-, and cold-induced regulation. These results might supply some hints for the functional diversity mechanisms of DbGAPDH, and fresh information for further research to bridge the gap between our knowledge of DNA and protein structure and our understanding of functional biology in GAPDH regulation.

•Performing bioaugmented inoculation with native strains in Daqu fermentation at industrial scale.•Traditional and bioaugmented Daqu fermentation process exist highly similar dynamics.•Microbiota in traditional and bioaugmented Daqu show no significant differences.•Slightly higher microbial richness in the bioaugmented fermentation process.Daqu, a traditional fermentation starter that is used for Chinese liquor and vinegar production, is still manufactured through a traditional spontaneous solid-state fermentation process with no selected microorganisms are intentionally inoculated. The aim of this work was to analyze the microbiota dynamics during the solid-state fermentation process of Daqu using a traditional and bioaugmented inoculation with autochthonous of Bacillus, Pediococcus, Saccharomycopsis and Wickerhamomyces at an industrial scale. Highly similar dynamics of physicochemical parameters, enzymatic activities and microbial communities were observed during the traditional and bioaugmented solid-state fermentation processes. Both in the two cases, groups of Streptophyta, Rickettsiales and Xanthomonadales only dominated the first two days, but Bacillales and Eurotiales became predominant members after 2 and 10 days fermentation, respectively. Phylotypes of Enterobacteriales, Lactobacillales, Saccharomycetales and Mucorales dominated the whole fermentation process. No significant difference (P > 0.05) in microbial structure was observed between the traditional and bioaugmented fermentation processes. However, slightly higher microbial richness was found during the bioaugmented fermentation process after 10 days fermentation. Our results reinforced the microbiota dynamic stability during the solid-state fermentation process of Daqu, and might aid in controlling the traditional Daqu manufacturing process.