Journal of Microbiology

Journal Article

Short-term effects of returning granulated straw on soil microbial community and organic carbon fractions in dryland farming: Wei Fan , Jinggui Wu; J. Microbiol. 2020;58(8):657-667. Published online June 25, 2020; DOI: https://doi.org/10.1007/s12275-020-9266-5

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Abstract: We conducted a 2-year field experiment which was comprised of five treatments, namely no straw returning (CK), straw mulching (SM), straw plowed into the soil (SP), and straw returned in granulated form (SG). The aim of this study was to investigate the effects of different straw returning modes on soil bacterial and fungal community structure and their relationships to soil organic carbon (SOC) fractions at three different soil depths (0–20, 20–40, and 40–60 cm) in a dryland under maize cultivation in Northeast (NE) China. SM, SP, and SG treatments significantly increased SOC content. Compared with SM and SP treatments, SG treatment significantly increased the content of SOC and easily oxidizable carbon (EOC) in the topsoil (0–20 cm depth), and increased dissolved organic carbon (DOC) and SOC content of the light fraction (LFOC) in the 20–40 cm layer. Meanwhile, SG treatment exhibited the highest microbial biomass C (MBC) content in all of the three soil depths. SG treatment also enhanced bacterial richness as well as fungal richness and diversity in the upper 40 cm of soil. In addition, SG treatment increased the relative abundance of Proteobacteria in all depths, and had the highest relative abundance of Basidiomycota in the first 20 cm of soil. SP treatment showed the lowest soil organic carbon content in all fractions and soil microbial community composition. SM treatment exhibited similar results to SG treatment in SOC, DOC, and LFOC contents, and bacterial diversity in the topsoil and subsoil. As a whole, treatment SG improved soil quality and maize yield, hence we recommend returning granulated straw as the most effective practice for enhancing labile SOC fractions as well as maintaining soil diversity and microbial richness of arid farmlands in NE China.

Histological Alterations and Immune Response Induced by Pet Toxin During Colonization with Enteroaggregative Escherichia coli (EAEC) in a Mouse Model: Teresita Sainz , Julia Perez , Ma. Cristina Fresan , Veronica Flores , Luis Jimenez , Ulises Hernandez , Ismael Herrera , Carlos Eslava; J. Microbiol. 2002;40(2):91-97.

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Abstract: Enteroaggregative E. coli (EAEC) is an important aethiological causal agent of diarrhea in people of developed and undeveloped countries. Different in vitro and in vivo models have been proposed to study the pathogenic and immune mechanisms of EAEC infection. The aim of this study was to analyze whether BALB/c mice could be used as an animal model to study EAEC pathogenesis. Six-week-old BALB/c mice were inoculated with EAEC strain 042 (O44:H18) nalidixic acid resistant, and re-inoculated ten days after. Mice feces were monitored for the presence of the EAEC strain over a period of 20 days. Bacteria were enumerated on MacConkey agar containing 100 ug of nalidixic acid per ml. Results showed that 35% of the animals were colonized for 3 days, 15% for 5 and 10% for more than 7 days. After re-inoculation only 16% of the animals remained colonized for more than 3 days. During the necropsy, the intestinal fluid of some of the infected animals presented mucus and blood. Six of these fluids showed the presence of IgA antibodies against Pet toxin and IgG antibodies raised against the toxin were also detected in the animal serum. Histopathologic evidence confirms the stimulation of mucus hypersecretion, an increased amount of goblet cells and the presence of bacterial aggregates in the apical surfaces of intestinal epithelial cells. Edema was present in the submucosa. These results suggest that BALB/c mice could be used as an animal model for the in vivo study of EAEC infection.

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