Divergent assembly of soil microbial necromass from microbial and organic fertilizers in Chimonobambusa hejiangensis forest.

Introduction: Variability in microbial residues within soil aggregates are becoming progressively essential to the nutritive and sustainability of soils, and are therefore broadly regarded as an indispensable part of soil organic matter. It is unexplored how the widespread implementation of microbial fertilisers in agricultural production impacts soil organic nutrients, in particular the microbial residue fraction. Methods: We performed a three-year field experiment to verify the distinct impacts of microbial and organic fertilizers on carbon accumulation in soil microbial leftovers among aggregate fractions. Results: Microbial residual carbon was shown to decrease insignificantly during the application of microbial fertilizer and to rise marginally afterwards with the utilization of organic fertilizer. However, the combined effects of the two fertilizers had substantial impacts on the accumulation of microbial residual carbon. Changes in the structure of the fungi and bacteria shown in this study have implications for the short-term potential of microbial fertilizer shortages to permanent soil carbon sequestration. Additionally, our findings revealed variations in microbial residue accumulation across the microbial fertilizers, with Azotobacter chroococcum fertilizer being preferable to Bacillus mucilaginosus fertilizer due to its higher efficiency. In this scenario of nutrient addition, fungal residues may serve as the primary binding component or focal point for the production of new microaggregates, since the quantity of SOC provided by fungal residues increased while that supplied by bacterial residues decreased. Discussion: Our findings collectively suggested that the mechanisms behind the observed bacterial and fungal MRC (microbial residue carbon) responses to microbial fertilizer or organic fertilizer in bamboo forest soils are likely to be distinct. The application of microbial fertilizers for a limited duration led to a decline soil stable carbon pool, potentially influencing the regulation of soil nutrients in such hilly bamboo forests.

Dynamic Changes in Flavor and Microbiota in Traditionally Fermented Bamboo Shoots (Chimonobambusa szechuanensis (Rendle) Keng f.).

Dissecting flavor formation and microbial succession during traditional fermentation help to promote standardized and large-scale production in the sour shoot industry. The principal objective of the present research is to elucidate the interplay between the physicochemical attributes, flavor, and microbial compositions of sour bamboo shoots in the process of fermentation. The findings obtained from the principal component analysis (PCA) indicated notable fluctuations in both the physicochemical parameters and flavor components throughout the 28 day fermentation process. At least 13 volatile compounds (OAV > 1) have been detected as characteristic aroma compounds in sour bamboo shoots. Among these, 2,4-dimethyl Benzaldehyde exhibits the highest OAV (129.73~668.84) and is likely the primary contributor to the sour odor of the bamboo shoots. The analysis of the microbial community in sour bamboo shoots revealed that the most abundant phyla were Firmicutes and Proteobacteria, while the most prevalent genera were Enterococcus, Lactococcus, and Serratia. The results of the correlation analysis revealed that Firmicutes exhibited a positive correlation with various chemical compounds, including 3,6-nonylidene-1-ol, 2,4-dimethyl benzaldehyde, silanediol, dimethyl-, nonanal, and 2,2,4-trimethyl-1,3-pentylenediol diisobutyrate. Similarly, Lactococcus was found to be positively correlated with several chemical compounds, such as dimethyl-silanediol, 1-heptanol, 3,6-nonylidene-1-ol, nonanal, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, dibutyl phthalate, and TA. This study provides a theoretical basis for the standardization of traditional natural fermented sour bamboo production technology, which will help to further improve the flavor and quality of sour bamboo.

Enhanced enzyme thermostability of a family I.3 lipase LipSR1 by T118A mutation at the calcium-binding site.

OBJECTIVES: The lipase gene lipSR1 isolated from oil-contaminated soil exhibits high hydrolytic activity for short-chain fatty acid substrates. A single calcium ion is required to anchor the lid of LipSR1 in an open conformation by coordination with two aspartate residues and three other residues in the lid. The lid of LipSR1 is anchored by Ca2+, which is coordinated by side-chain carboxyl oxygens of Asp153 and Asp157, carbonyl oxygens of Thr118 and Ser144, and the side chain of Gln120. RESULTS: D157A, D153R, Q120A, S144A, and T118A mutants were produced by site-directed mutagenesis in this study. Analyses of hydrolytic activity and thermostability showed that the properties of D157A, D153R, Q120A, and S144A were almost lost, suggesting that Asp157, Asp153, Gln120, and Ser144 are important residues for LipSR1. However, the catalytic performance of T118A was clearly maintained. Moreover, the thermostability of mutant T118A was higher than that of wild-type LipSR1. CONCLUSIONS: These results indicated that mutation of threonine at position 118 improved the stability of the enzyme at high temperature.

Reduction of pyocyanin synthesis and antibiotic resistance in Pseudomonas aeruginosa by low concentration ethanol.

Pseudomonas aeruginosa is a common bacteria that may cause a wide range of severe illnesses in humans. One of the nonantibiotic therapies, antivirulence factor therapy, has attracted ongoing interest. Screening for and investigating bacterial virulence factor inhibitors is critical for the development of antivirulence factor treatments. Pyocyanin is P. aeruginosa's distinctive pigment, and it plays a key role in infection. The impact of low concentration ethanol on pyocyanin production was investigated in this research. Pyocyanin production was found both subjectively and quantitatively. The effects of ethanol on the expression of pyocyanin production genes were studied using qRT-PCR and western blotting. The findings demonstrated that low concentrations of ethanol (as little as 0.1%) greatly suppressed pyocyanin production without affecting P. aeruginosa growth. The degree of inhibition increased as the ethanol contentration rose. Ethanol inhibits the expression of genes involved in pyocyanin production. This inhibitory impact was mostly seen at the protein level. Further research revealed that ethanol increased the expression of the post-transcriptional regulator RsmA, which inhibits pyocyanin production. Given the favorable relationship between pyocyanin production and antibiotic resistance, the impact of low concentration ethanol on various antibiotics was investigated. Ethanol lowered antibiotic resistance in P. aeruginosa, presumably by inhibiting pyocyanin.

Biodegradation of Oil by a Newly Isolated Strain Acinetobacter junii WCO-9 and Its Comparative Pan-Genome Analysis.

Waste oil pollution and the treatment of oily waste present a challenge, and the exploitation of microbial resources is a safe and efficient method to resolve these problems. Lipase-producing microorganisms can directly degrade waste oil and promote the degradation of oily waste and, therefore, have very significant research and application value. The isolation of efficient oil-degrading strains is of great practical significance in research into microbial remediation in oil-contaminated environments and for the enrichment of the microbial lipase resource library. In this study, Acinetobacter junii WCO-9, an efficient oil-degrading bacterium, was isolated from an oil-contaminated soil using olive oil as the sole carbon source, and its enzyme activity of ρ-nitrophenyl decanoate (ρ-NPD) decomposition was 3000 U/L. The WCO-9 strain could degrade a variety of edible oils, and its degradation capability was significantly better than that of the control strain, A junii ATCC 17908. Comparative pan-genome and lipid degradation pathway analyses indicated that A. junii isolated from the same environment shared a similar set of core genes and that the species accumulated more specific genes that facilitated resistance to environmental stresses under different environmental conditions. WCO-9 has accumulated a complete set of oil metabolism genes under a long-term oil-contamination environment, and the compact arrangement of abundant lipase and lipase chaperones has further strengthened the ability of the strain to survive in such environments. This is the main reason why WCO-9 is able to degrade oil significantly more effectively than ATCC 17908. In addition, WCO-9 possesses a specific lipase that is not found in homologous strains. In summary, A. junii WCO-9, with a complete triglyceride degradation pathway and the specific lipase gene, has great potential in environmental remediation and lipase for industry.

Epigenetic and somaclonal divergence in Dendrocalamus farinosus for physiological augmentation and lignin degradation.

Epigenetic and molecular variation is a key approach for the improvement of plants. From in vitro tissue culture of Dendrocalamus farinosus; 30 plants were regenerated and after 2 years, the physiological, biochemical, and genomic studies were conducted. The results highlighted that for all phenotypic characteristics, the 30 regenerated plants were superior in comparison with the control (CK). From genetical analysis, a total of 97 bands were witnessed ranging between 212 bp and 2.2 kb. The results for OPU14 showed one additional specific band (723 bp) and one band (700 bp) were missing. The 10 plants were having genetic variability and can be termed as somaclones while the other plants have epigenetic variations. The cellulose and lignin analysis highlighted that somaclone No. 30 has the least cellulose content of 35%; while the somaclones No. 102 and No. 213 have the least 3.21% and 3.48% of lignin contents. Therefore, somaclones No. 30, No. 102, and No. 213 were selected for the histochemical localization. The lignin investigation revealed that somaclone No. 30 is greater while somaclones No. 102 and No. 213 were reduced in vascular bundles in comparison with the CK along with the high expression level of 4CL, C3H, C4H, COMT, and CCoAOMT1 genes.

Differential responses of soil hydrolytic and oxidative enzyme activities to the natural forest conversion.

Effects of natural forest conversion (NFC) on soil nutrient turnover are substantially mediated by soil microbial extracellular hydrolytic enzymatic activities (Hy-EEAs) and oxidative enzymatic activities (Ox-EEAs). Yet it remains largely unknown the indicative links between soil Hy- and Ox-EEAs and soil carbon (C), nitrogen (N) and phosphorus (P) supplies based on economic theories of microbial metabolism under NFC. Here we used a meta-analysis approach to synthesize the responses of the soil C-, N-, P-degrading Hy-EEAs and Ox-EEAs, soil microbial biomass, soil organic C, total N, P and available P parameters to natural forest conversion from 51 peer-reviewed studies. Our results showed that NFC notably decreased soil Hy-EEAs but statistically insignificant reduction of soil Ox-EEAs. The changes of soil Hy- and Ox-EEAs were significantly and positively associated with soil organic C, available P as well as microbial biomass C and N but significantly and negatively correlated with soil pH, whereas the changes of soil C/N impacted on soil Ox-EEAs remarkably but not for soil Hy-EEAs. The depletion of soil organic carbon stimulated soil microbial secretion of Hy- and Ox-EEAs. The soil total N scarcity only provoked soil microbial Hy-EEAs rather than Ox-EEAs. The soil total P dearth quickened the soil Ox-EEAs, however, the plenitude of soil available P suppressed soil Hy- and Ox-EEAs. Moreover, the eco-enzymatic stoichiometry of soil Hy-EEAs indicated that soil N and P nutrient limitation after NFC restricted soil microbial N- and P-acquiring enzymes secretion, which ultimately reduced resources availability for C acquisition. Altogether, the distinct responses of soil Hy- and Ox-EEAs depended on substrate availability peculiarly for soil N and P gains of microorganisms for further enzymatic ability on soil C decomposition and highlighted the abundant or absent supply of soil N and P for positive or negative enzymatic activities on metabolic requirement of soil edaphons.

Effects of exotic plantation forests on soil edaphon and organic matter fractions.

There is uncertainty and limited knowledge regarding soil microbial properties and organic matter fractions of natural secondary forest accompanying chemical environmental changes of replacement by pure alien plantation forests in a hilly area of southwest of Sichuan province China. The aim of this study was to evaluate the impact of natural secondary forest (NSF) to pure Cryptomeria fortunei forest (CFF) and Cunninghamia lanceolata forest (CLF) on soil organic fractions and microbial communities. The results showed that the soil total phospholipid fatty acids (PLFAs), total bacteria and fungi, microbial carbon pool, organic recalcitrant carbon (C) and (N) fractions, soil microbial quotient and labile and recalcitrant C use efficiencies in each pure plantation were significantly decreased, but their microbial N pool, labile C and N pools, soil carbon dioxide efflux, soil respiratory quotient and recalcitrant N use efficiency were increased. An RDA analysis revealed that soil total PLFAs, total bacteria and fungi and total Gram-positive and Gram-negative bacteria were significantly associated with exchangeable Al3+, exchangeable acid, Al3+, available P and Mg2+ and pH, which resulted into microbial functional changes of soil labile and recalcitrant substrate use efficiencies. Modified microbial C- and N-use efficiency due to forest conversion ultimately meets those of rapidly growing trees in plantation forests. Enlarged soil labile fractions and soil respiratory quotients in plantation forests would be a potential positive effect for C source in the future forest management. Altogether, pure plantation practices could provoke regulatory networks and functions of soil microbes and enzyme activities, consequently leading to differentiated utilization of soil organic matter fractions accompanying the change in environmental factors.

[Transcriptome analysis and gene function annotation of Bambusa emeiensis shoots based on high-throughput sequencing technology].

Bambusa emeiensis is one of the preponderant species of sympodial bamboos in Sichuan province of China, and has excellent fiber length and quality as raw materials for papermaking, textile and other industries. In this study, with the application of Illumina HiSeq™ 2000 platform, we analyzed transcriptome in B. emeiensis with different heights of 10, 50, 100 and 150 cm. A total of 69.28 M reads were obtained, and a sum up of 111 137 bands of Unigenes were acquired following de novo stitching, assembly and clustering, among which there were 63 094 bands that had been integrated in the COG, GO, KEGG, Swiss-Prot and Nr databases using annotated methods. These Unigenes not only had general functions, such as transcription and signal transduction, but were also involved in sucrose transport and metabolism, secondary metabolites and cell wall biosynthesis. There was significant difference regarding the expression of cellulose synthase gene in B. emeiensis at different heights, relevant genes were found that might be responsible for the regulation of the growth and development of B. emeiensis as well as the biosynthesis of cellulose and lignin. Our findings could provide some elementary theories for breed improvement of B. emeiensis.