Journal of Microbiology

Journal Article

The relationship between bacterial diversity and organic carbon mineralization in soft rock and sand compound soil: Zhen Guo , Juan Li , Lei Ge , Chenxi Yang , Jichang Han; J. Microbiol. 2020;58(9):750-760. Published online July 24, 2020; DOI: https://doi.org/10.1007/s12275-020-0130-4

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The soil organic carbon (SOC) mineralization rate in sandy soil plays an important role in improving soil quality, and a research is needed to determine management practices that optimize the mineralization rate. When sandy soil is improved by adding soft rock, the specific promotion process of bacterium to SOC mineralization remain unclear. To investigate these mechanisms, we selected four treatments with soft rock to sand volume ratios of 0:1 (CK), 1:5 (C1), 1:2 (C2) and 1:1 (C3) to study. The mineralization rate of organic carbon was measured using the lye absorption method. Highthroughput sequencing and scanning electron microscopy were used to determine the bacterial community structure and soil microstructure, respectively. The results showed that the organic carbon content of the sandy soil increased significantly (182.22–276.43%) after using the soft rock treatments. The SOC mineralization rate could be divided into two stages: a rapid decline during days 1–8 and a slow decline during days 8–60. With increased incubation time, the intensity of the cumulative release of organic carbon gradually weakened. Compared with the CK treatment, the SOC mineralization accumulation (Ct) and the potential mineralizable organic carbon content (C0) in the C1, C2, and C3 treatments increased significantly, by 106.98–225.94% and 112.22– 254.08%, respectively. The cumulative mineralization rate (Cr) was 18.11% and 21.38% smaller with treatments C2 and C3, respectively. The SOC mineralization rate constant (k) decreased significantly after the addition of soft rock, while the half-turnover period (Th) changed inversely with k. Compared with the CK treatment, the number of gene copies of the soil bacteria increased by 15.38–272.53% after adding soft rock, with the most significant increase in treatment C3. The bacterial diversity index also increased significantly under treatment C3. The three dominant bacteria were Proteobacteria, Actinobacteria, and Chloroflexi. The correlation between Cr and one of the non-dominant bacteria, Firmicutes, was large, and the bacteria had a significant positive correlation with k. At the same time, the abundance of Firmicutes under treatments C2 and C3 was small. As the proportion of soft rock increased, the soil particles changed from point contact to surface contact, and the adhesion on the surface of the particles gradually increased. Results from this study show that the retention time of SOC can be increased and the carbon sequestration effect is better when the ratio of soft rock to sand is set to 1:2.

Citations

Citations to this article as recorded by

Siltation of check dams alters microbial communities and thus limits organic carbon mineralization
Xiaojun Liu, Yi Zhang, Peng Li, Lie Xiao
Soil and Tillage Research.2024; 236: 105949. CrossRef
Tree species mixing enhances rhizosphere soil organic carbon mineralization of conifers in subtropical plantations
Wen-Qing Li, Zi-Jun Wu, Ying-Ying Zong, G. Geoff Wang, Fu-Sheng Chen, Yuan-Qiu Liu, Jian-Jun Li, Xiang-Min Fang
Forest Ecology and Management.2022; 516: 120238. CrossRef
Response of soil structure and crop yield to soft rock in Mu Us sandy land, China
Jian Zhang, Zhen Guo
Scientific Reports.2022;[Epub] CrossRef

Research Support, Non-U.S. Gov'ts

Identification of Conserved Surface Proteins as Novel Antigenic Vaccine Candidates of Actinobacillus pleuropneumoniae: Xiabing Chen , Zhuofei Xu , Lu Li , Huanchun Chen , Rui Zhou; J. Microbiol. 2012;50(6):978-986. Published online December 30, 2012; DOI: https://doi.org/10.1007/s12275-012-2214-2

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Abstract: Actinobacillus pleuropneumoniae is an important swine respiratory pathogen causing great economic losses worldwide. Identification of conserved surface antigenic proteins is helpful for developing effective vaccines. In this study, a genome-wide strategy combined with bioinformatic and experimental approaches, was applied to discover and characterize surface-associated immunogenic proteins of A. pleuropneumoniae. Thirty nine genes encoding outer membrane proteins (OMPs) and lipoproteins were identified by comparative genomics and gene expression profiling as beinghighly conserved and stably transcribed in the different serotypes of A. pleuropneumoniae reference strains. Twelve of these conserved proteins were successfully expressed in Escherichia coli and their immunogenicity was estimated by homologous challenge in the mouse model, and then three of these proteins (APJL_0126, HbpA and OmpW) were further tested in the natural host (swine) by homologous and heterologous challenges. The results showed that these proteins could induce high titers of antibodies, but vaccination with each protein individually elicited low protective immunity against A. pleuropneumoniae. This study gives novel insights into immunogenicity of the conserved OMPs and lipoproteins of A. pleuropneumoniae. Although none of the surface proteins characterized in this study could individually induce effective protective immunity against A. pleuropneumoniae, they are potential candidates for subunit vaccines in combination with Apx toxins.

Structural and Functional Importance of Outer Membrane Proteins in Vibrio cholerae Flagellum: Wasimul Bari , Kang-Mu Lee , Sang Sun Yoon; J. Microbiol. 2012;50(4):631-637. Published online August 25, 2012; DOI: https://doi.org/10.1007/s12275-012-2116-3

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Abstract: Vibrio cholerae has a sheath-covered monotrichous flagellum that is known to contribute to virulence. Although the structural organization of the V. cholerae flagellum has been extensively studied, the involvement of outer membrane proteins as integral components in the flagellum still remains elusive. Here we show that flagella produced by V. cholerae O1 El Tor strain C6706 were two times thicker than those from two other Gram-negative bacteria. A C6706 mutant strain (SSY11) devoid of two outer membrane proteins (OMPs), OmpU and OmpT, produced thinner flagella. SSY11 showed significant defects in the flagella-mediated motility as compared to its parental strain. Moreover, increased shedding of the flagella-associated proteins was observed in the culture supernatant of SSY11. This finding was also supported by the observation that culture supernatants of the SSY11 strain induced the production of a significantly higher level of IL-8 in human colon carcinoma HT29 and alveolar epithelial A549 cells than those of the wild-type C6706 strain. These results further suggest a definite role of these two OMPs in providing the structural integrity of the V. cholerae flagellum as part of the surrounding sheath.

Journal Article

Proteomic Analysis of Outer Membrane Proteins from Acinetobacter baumannii DU202 in Tetracycline Stress Condition: Sung-Ho Yun , Chi-Won Choi , Soon-Ho Park , Je Chul Lee , Sun-Hee Leem , Jong-Soon Choi , Soohyun Kim , Seung Il Kim; J. Microbiol. 2008;46(6):720-727. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0202-3

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Abstract: Acinetobacter baumannii readily developed antimicrobial resistance to clinically available antibiotics. A. baumannii DU202 is a multi-drug resistant strain, and is highly resistant to tetracycline (MIC>1,024μg/ml). The surface proteome of A. baumannii DU202 in response to the sub-minimal inhibitory concentration (subMIC) of tetracycline was analyzed by 2-DE/MS-MS and 1-DE/LC/MS-MS to understand the pathways that form barriers for tetracycline. Membrane expression of major outer membrane proteins (Omps) was significantly decreased in response to the subMIC of tetracycline. These Omps with sizes of 38, 32, 28, and 21 kDa were identified as OmpA38, OmpA32, CarO, and OmpW, respectively. However, transcription level of these Omps was not significantly changed. 1-DE/LC/MS-MS analysis of secreted proteins showed that OmpA38, CarO, OmpW, and other Omps were increasingly secreted at tetracycline condition. This result suggests that A. baumannii actively regulates the membrane expression and the secretion of Omps to overcome antibiotic stress condition.

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