This study examined and compared the microbial community in three typical fermentation starters (called as Daqu, Xiaoqu, and Fuqu in China) used for liquor production by analysing the 16S and 18S rRNA gene clone library. The results show that the microbial diversity in the three types of fermentation starters (JiuQu) differs significantly. The bacterial species in Daqu and Fuqu were mainly thermophilic or thermotolerant. In Daqu, the dominant bacterial species were Thermoactinomyces sanguinis (53.85%) and Pantoea agglomerans (19.23%), followed by uncultured bacteria (15.39%). The lactic acid bacterium Weissella cibaria (50%) and a member of Enterobacteriaceae, Enterobacter ludwigii (10%), were the dominant bacterial species in Xiaoqu. Low abundances of other bacteria, including Deinococcus radiodurans, Corynebacterium variabile and Acinetobacter baumannii, were reported for Xiaoqu. Enterococcus faecium, Clostridium beijerinckii and Bacillus cereus were observed in Fuqu and accounted for 46.67, 23.33 and 16.67% of the total bacteria identified, respectively. Fungal diversity was high in Daqu and consisted exclusively of thermophilic moulds, such as Aspergillus glaucus (62.5%), Thermomyces lanuginosus (12.5%) and Thermoascus crustaceus (12.5%). Only two fungal species were reported for Fuqu and Xiaoqu and both contained the mould Rhizopus oryzae. Saccharomyces cerevisiae and the non-Saccharomyces yeast (Saccharomycopsis fibuligera) were also identified in Fuqu and Xiaoqu, respectively. This finding suggests that microbial community structure in JiuQu starters is the key factor to determine the variety of flavours.
Land application of animal manure is a common agricultural practice potentially leading to dispersal and propagation of antibiotic resistance genes (ARGs) in environmental settings. However, the fate of resistome in agro-ecosystems over time following application of different manure sources has never been compared systematically. Here, soil microcosm incubation was conducted to compare effects of poultry, cattle and swine manures spiked with or without the antibiotic tylosin on the temporal changes of soil ARGs. The high-throughput quantitative PCR detected a total of 185 unique ARGs, with Macrolide-Lincosamide-Streptogramin B resistance as the most frequently encountered ARG type. The diversity and abundance of ARGs significantly increased following application of manure and manure spiked with tylosin, with more pronounced effects observed in the swine and poultry manure treatments than in the cattle manure treatment. The level of antibiotic resistance gradually decreased over time in all manured soils but was still significantly higher in the soils treated with swine and poultry manures than in the untreated soils after 130 days' incubation. Tylosin-amended soils consistently showed higher abundances of ARGs than soils treated with manure only, suggesting a strong selection pressure of antibiotic-spiked manure on soil ARGs. The relative abundance of ARGs had significantly positive correlations with integrase and transposase genes, indicative of horizontal transfer potential of ARGs in manure and tylosin treated soils. Our findings provide evidence that application of swine and poultry manures might enrich more soil ARGs than cattle manure, which necessitates the appropriate treatment of raw animal manures prior to land application to minimise the spread of environmental ARGs.
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