Diversity Of Indigenous Bacteria Research Articles

Remediation of Cr(VI)-Contaminated Soil by Biochar-Supported Nanoscale Zero-Valent Iron and the Consequences for Indigenous Microbial Communities.

Biochar/nano-zero-valent iron (BC-nZVI) composites are currently of great interest as an efficient remediation material for contaminated soil, but their potential to remediate Cr-contaminated soils and effect on soil microecology is unclear. The purpose of this study was to investigate the effect of BC-nZVI composites on the removal of Cr(VI) from soil, and indigenous microbial diversity and community composition. The results showed that after 15 days of remediation with 10 g/kg of BC-nZVI, 86.55% of Cr(VI) was removed from the soil. The remediation of the Cr-contaminated soil with BC-nZVI resulted in a significant increase in OTUs and α-diversity index, and even a significant increase in the abundance and diversity of indigenous bacteria and unique bacterial species in the community by reducing the toxic concentration of Cr, changing soil properties, and providing habitat for survival. These results confirm that BC-nZVI is effective in removing Cr(VI) and stabilizing Cr in soil with no significant adverse effects on soil quality or soil microorganisms.

Diversity of indigenous bacteria in fermented dough with Saccharomyces cerevisiae Y10 and Torulaspora delbrueckii Y22

There is a great diversity of indigenous microorganisms in flour, the number of which increased greatly during long-term dough fermentation, affecting dough fermentation and product quality. In this study, the diversity of indigenous bacteria in fermented dough inoculated with single Saccharomyces cerevisiae Y10 strain, Torulaspora delbrueckii Y22 strain and their co-culture was revealed by Illumina MiSeq sequencing. Compared with the dough without yeast inoculation, the bacteria diversity in yeast fermented dough was lower after 12 h fermentation. However, the abundance of lactic acid bacteria (LAB) in the dough inoculated with yeast was higher than that in dough without any yeast inoculated. Similar community structures of bacteria were found in doughs inoculated with different yeast, but their abundance were different. The abundance of the genus Clostridium in doughs inoculated with single S. cerevisiae Y10 was lower than non-inoculated dough, doughs inoculated with T. delbrueckii Y22 and co-culture of S. cerevisiae Y10 and T. delbrueckii Y22 at the same fermentation stage. In comparison with the dough without yeast inoculation, the presence of T. delbrueckii Y22 and the co-culture of S. cerevisiae Y10 and T. delbrueckii Y22 decreased the relative abundance of Staphylococcus, Cronobacter and Enterobacter in fermented dough. Furthermore, the relative abundance of Komagataeibacter increased in the presence of co-culture of S. cerevisiae Y10 and T. delbrueckii Y22. The results of this study suggested that the diversity of indigenous bacteria during dough fermentation was greatly influenced by the starter strain.

Comparative analysis of bacterial community and functional species in oil reservoirs with different in situ temperatures.

Temperature is supposed to be one of the primary drivers for the bacterial diversification as well as hydrocarbon formation process of oil reservoirs. However, the bacterial community compositions are not systematically elucidated in oil reservoirs with different temperatures. Herein, the diversity of indigenous bacteria and the functional species in the water samples from oil reservoirs with different in situ temperatures was investigated by high-throughput sequencing technology. The results showed that samples in the high (65°C) and super high (80°C) temperature oil reservoir had significantly high bacterial richness, even more than twice as much as moderate temperature (36°C) ones, which showed relatively high bacterial diversity. Meanwhile, the bacterial compositions were almost similar in the high temperature oil reservoirs but there were different relative abundances of the bacterial communities. Phylogenetic analysis revealed that indigenous bacteria fell into 20 phylotypes in which Proteobacteria were the principal phylum in all of samples. At the genus level, 10 out of 22 major genera displayed statistically significant differences. Among of them, Pseudomonas was extremely dominant in all of samples, while Halomonas, Caldicoprobacter, Arcobacter, and Marinobacter tended to be enriched in the high temperature oil reservoirs. Moreover, the abundance of bacterial populations exhibited important distinction in oil reservoir such as hydrocarbon-oxidizing, fermentative, nitrate-reducing, sulfate-reducing, and methanogenic bacteria. Those bacteria were strongly correlated to in situ temperature variation.

Molecular tools in rhizosphere microbiology—from single-cell to whole-community analysis

It is the aim of this chapter to present an overview of new, molecular tools that have been developed over recent years to study individual, single cells and composite, complex communities of microorganisms in the rhizosphere. We have carefully focused on culture-independent assays and selected methodologies that have already been or will soon be applicable for rhizosphere microbiology. Emphasis is placed on rhizosphere bacteria and the review first describes a number of the new methodologies developed for detection and localization of specific bacterial populations using modern electron and fluorescence microscopy combined with specific tagging techniques. First half of the chapter further comprises a thorough treatise of the recent development of reporter gene technology, i.e. using specific reporter bacteria to detect microscale distributions of rhizosphere compounds such as nutrients, metals and organic exudates or contaminants. Second half of the chapter devoted to microbial community analysis contains a thorough treatise of nucleotide- and PCR-based technologies to study composition and diversity of indigenous bacteria in the natural rhizosphere. Also included are the most recent developments of functional gene and gene expression analyses in the rhizosphere based on specific mRNA transcript or transcriptome analysis, proteome analysis and construction of metagenomic libraries.