Antimony (Sb) and copper (Cu) are toxic heavy metals that are associated with a wide variety of minerals. Sb(III)-oxidizing bacteria that convert the toxic Sb(III) to the less toxic Sb(V) are potentially useful for environmental Sb bioremediation. A total of 125 culturable Sb(III)/Cu(II)-resistant bacteria from 11 different types of mining soils were isolated. Four strains identified as Arthrobacter, Acinetobacter and Janibacter exhibited notably high minimum inhibitory concentrations (MICs) for Sb(III) (>10 mM),making them the most highly Sb(III)-resistant bacteria to date. Thirty-six strains were able to oxidize Sb(III), including Pseudomonas-, Comamonas-, Acinetobacter-, Sphingopyxis-, Paracoccus- Aminobacter-, Arthrobacter-, Bacillus-, Janibacter- and Variovorax-like isolates. Canonical correspondence analysis (CCA) revealed that the soil concentrations of Sb and Cu were the most obvious environmental factors affecting the culturable bacterial population structures. Stepwise linear regression was used to create two predictive models for the correlation between soil characteristics and the bacterial Sb(III) or Cu(II) resistance. The concentrations of Sb and Cu in the soil was the significant factors affecting the bacterial Sb(III) resistance, whereas the concentrations of S and P in the soil greatly affected the bacterial Cu(II) resistance. The two stepwise linear regression models that we derived are as follows: and [where the MICSb(III) and MICCu(II) represent the average bacterial MIC for the metal of each soil (µM), and the CSb, CCu, CS and CP represent concentrations for Sb, Cu, S and P (mg/kg) in soil, respectively, p<0.01]. The stepwise linear regression models we developed suggest that metals as well as other soil physicochemical parameters can contribute to bacterial resistance to metals.
The current understanding of human gut microbial community is mainly limited to taxonomic features at the genus level. Here, we examined the human gut microbial community at the species level by metataxonomics. To achieve this purpose, a high-throughput approach involving operational phylogenetic unit analysis of the near full-length 16S ribosomal RNA (rRNA) gene sequence was used. A total of 1,235 species-level phylotypes (SLPs) were classified in the feces of 120 Chinese healthy individuals, including 461 previously classified species, 358 potentially new species, and 416 potentially new taxa, which were categorized into low, medium, and high prevalent bacteria groups based on their prevalence. Each individual harbored 186 ± 51 SLPs on average. There was no universal bacterial species shared by all the individuals. However, 90 ± 19 of 116 SLPs were shared in the high prevalent bacteria group. Thirty-two out of thirty-eight species in the high prevalent bacteria group detected in this study were also found in at least one previous study on human gut microbiota based on either culture-dependent or culture-independent approaches. Through compositional analysis, a hierarchical clustering of the prevalence and relative abundance of the 1,235 SLPs revealed two types of gut microbial communities, which were dominated by Prevotella copri and Bacteroides vulgatus, respectively. The type dominated by P. copri was more prevalent in northern China, while the B. vulgatus-dominant type was more prevalent in southern China. Therefore, P-and B-type gut microbial communities in China were proposed. It was found that 166 out of 461 known bacterial species have been previously reported as potential pathogens, and the individuals sampled for this study harbored 20 of these potential pathogenic species on average. The top two most abundant and prevalent potential pathogenic species were Klebsiella pneumoniae and Bacteroides fragilis.
A growth trial lasting for 12 weeks was conducted in a semi flow-through system to determine the dietary potassium requirement of juvenile grass carp (Ctenopharyngodon idellus) with an initial body weight of 4.8 g. Seven isonitrogenous and isoenergetic semi-purified diets were compounded with different dietary potassium levels: 1. 50, 2.32, 3.28, 5.30, 7.12, 9.45 and 10.44 g kg −1 diet. The results showed that specific growth rate and feed efficiency of grass carp were significantly (P b 0.05) affected by dietary potassium level, the highest value of specific growth rate was in 5.30 g kg −1 group and feed efficiency values in 5.30, 7.12 and 9.45 g kg −1 groups were significantly higher than those in the other groups. The survival rate of grass carp in the present study was not affected by dietary potassium level (P N 0.05). The Na + -K + ATPase activity value in the gills varied significantly (P b 0.05) with dietary potassium level and showed an increasing and then decreasing trend, and the highest value was in the 7.12 g kg −1 group. Dietary potassium level showed significant (P b 0.05) effect on serum SOD, ALP and AST activities. SOD and ALP activities increased and then decreased as potassium level increased, while AST decreased first and then increased. Serum TP and TC contents increased and then decreased with potassium level (P b 0.05). TG, ALT and BUN were not affected by dietary potassium level (P N 0.05). Body potassium and moisture contents increased and lipid content decreased with dietary potassium content, while ash content in fish body increased first and then decreased as potassium content increased (P b 0.05). Body protein in the 10.44 g kg −1 group was significantly lowered (P b 0.05). However, calcium, magnesium, phosphorus and sodium contents in dry matter were not affected by dietary potassium level. When the potassium content of water was 1.86-3.10 mg L −1 , judging from the polynomial regression analysis for the specific growth rate of fish and the Na + -K + ATPase activity in the gill, and the broken-line analysis for body potassium content, the optimal dietary potassium content for juvenile grass carp was 4.65, 7.27 and 5.98 g kg −1 diet respectively.
BackgroundMembers of Comamonas testosteroni are environmental microorganisms that are usually found in polluted environment samples. They utilize steroids and aromatic compounds but rarely sugars, and show resistance to multiple heavy metals and multiple drugs. However, comprehensive genomic analysis among the C. testosteroni strains is lacked.ResultsTo understand the genome bases of the features of C. testosteroni, we sequenced 10 strains of this species and analyzed them together with other related published genome sequences. The results revealed that: 1) the strains of C. testosteroni have genome sizes ranging from 5.1 to 6.0 Mb and G + C contents ranging from 61.1% to 61.8%. The pan-genome contained 10,165 gene families and the core genome contained 3,599 gene families. Heap’s law analysis indicated that the pan-genome of C. testosteroni may be open (α = 0.639); 2) by analyzing 31 phenotypes of 11 available C. testosteroni strains, 99.4% of the genotypes (putative genes) were found to be correlated to the phenotypes, indicating a high correlation between phenotypes and genotypes; 3) gene clusters for nitrate reduction, steroids degradation and metal and multi-drug resistance were found and were highly conserved among all the genomes of this species; 4) the genome similarity of C. testosteroni may be related to the geographical distances.ConclusionsThis work provided an overview on the genomes of C. testosteroni and new genome resources that would accelerate the further investigations of this species. Importantly, this work focused on the analysis of potential genetic determinants for the typical characters and found high correlation between the phenotypes and their corresponding genotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1314-x) contains supplementary material, which is available to authorized users.
The immune system is a biological process system that can detect a variety of non-self substances, such as viruses, bacteria, and parasites or abnormal substances, to distinguish them from healthy tissues of organism so as to prevent diseases. 1,2 Over the course of biological evolution, jawed vertebrates have developed two immune systems, namely innate immune system and adaptive immune system. Innate immunity is the earliest immune mechanism that protects the host from infection by pathogens in various means.Adaptive immunity is activated by innate immunity, and it is a highly specific, systematic and memory-based immune mechanism to eliminate pathogens and protect organisms. The immune systems in all the jawed vertebrates have some characteristics in common. For example they have a highly conserved innate immune systems, and innate immune system and adaptive immune system communicate and cooperate to protect host, but both immune systems develop separately. 3
A growth trial lasting for 12 weeks was conducted in 21 net cages to determine the dietary potassium (K) requirement of subadult grass carp (Ctenopharyngodon idellus) (Average weight: 331.3 g). Seven isonitrogenous and isoenergetic semi‐purified diets were compounded with different dietary K level. The specific growth rate (SGR) of fish was significantly (P < 0.05) improved by dietary K supplementation, SGR and the gill Na+‐K+ ATPase activity increased first and then decreased (P < 0.05) as dietary K level increased. The highest SGR and gill Na+‐K+ ATPase activity values were both observed at 6.38 g kg−1 group. Dietary K level showed significant (P < 0.05) effect on serum superoxide dismutase (SOD) and glucose (GLU), the maximum values of SOD and GLU were in 8.42 and 6.38 g kg−1 group, respectively. The body lipid content of the 6.38 g kg−1 group was significantly (P < 0.05) lower than that of the control. However, the ash content in the 8.42 g kg−1 group was significantly higher than those in the 1.21, 2.21, 4.41 and 6.38 g kg−1 group. When dietary protein was 320 g kg−1 and the waterborne potassium ranged from 6.86 to 9.10 mg L−1, the dietary K requirement for subadult grass carp judged from SGR and gill Na+‐K+ ATPase activity is 5.38 and 7.41 g kg−1 diet, respectively.
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