Canadian Journal of Microbiology
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Published By Canadian Science Publishing

1480-3275, 0008-4166

Author(s):  
Quanju Xiang ◽  
Juntao Zhang ◽  
Xiying Huang ◽  
Menggen Ma ◽  
Ke Zhao ◽  
...  

Silage fermentation, a sustainable way to use vegetable waste resources, is a complex process driven by a variety of microorganisms. We used lettuce waste as the main raw material for silage, analyzed changes in the physico-chemical characteristics and bacterial community composition of silage over a 60-day fermentation, identified differentially abundant taxa, predicted the functional profiles of bacterial communities, and determined the associated effects on the quality of silage. The biggest changes occurred in the early stage of silage fermentation. Changes in the physico-chemical characteristics included a decrease in pH and increases in ammonia nitrogen to total nitrogen ratio and lactic acid content. The numbers of lactic acid bacteria (LAB) increased and molds, yeasts and aerobic bacteria decreased. The bacterial communities and their predicted functions on day 0 were clearly different from those on day 7 to day 60. The relative abundances of phylum Firmicutes and genus Lactobacillus increased. Nitrite ammonification and nitrate ammonification were more prevalent after day 0. The differences in the predicted functions were associated with differences in pH and amino acid, protein, carbohydrate, NH3-N, ether extract and crude ash contents.


Author(s):  
Zhai Ligong ◽  
Liu Hongxia ◽  
Li Junjie ◽  
Zhaoxin Lu ◽  
Xiaomei Bie

Salmonella enterica serovars Paratyphi C is highly adapted to humans and can cause a typhoid-like disease with high mortality rates. In this study, three serovar-specific genes were determined for S. Paratyphi C, SPC_0871,SPC_0872, and SPC_0908, by comparative genomics method. Based on SPC_0908 and xcd gene for testing Salmonella spp., we have developed a duplex real-time nucleic acid sequence-based amplification (real-time NASBA) with molecular beacon approach for simultaneous detection of viable cells of Salmonella spp. and serotype Paratyphi C. The test selectively and consistently detected 53 Salmonella spp. (representing 31 serotypes) and 18 non-Salmonella strains. Additionally, the method showed high resistance to interference by natural background flora in pork and chicken samples. The sensitivity of the established approach was determined to be 4.89 CFU/25 g in artificially contaminated pork and chicken samples after pre-enrichment. We propose this NASBA-based protocol as a potential detection method for Salmonella spp. and serotype Paratyphi C in food of animal origin.


Author(s):  
Andrew Scott ◽  
Roger Murray ◽  
Yuan-Ching Tien ◽  
Edward Topp

The present study evaluated if enteric bacteria or antibiotic resistance genes carried in fecal amendments contaminate the hay at harvest, representing a potential route of exposure to ruminants that consume the hay. In field experiments, dairy manure was applied to a hay field for three successive growing seasons, and biosolids applied to a hay field for one growing season. Various enteric bacteria in the amendments were enumerated by viable plate count, and selected gene targets were quantified by qPCR. Key findings include the following: At harvest, hay receiving dairy manure or biosolids did not carry more viable enteric bacteria than did hay from unamended control plots. Fermentation of hay did not result in a detectable increase in viable enteric bacteria. The application of dairy manure or biosolids did result in a few gene targets being more abundant on hay at the first harvest. Fermentation of hay did result in an increase in the abundance of gene targets, but this occurred both with hay from amended and control plots. Overall, application of fecal amendments will result in an increase in the abundance of some gene targets associated with antibiotic resistance on first cut hay.


2022 ◽  
pp. 1-12
Author(s):  
Tomijiro Hara ◽  
Yumiko Takatsuka

In the Tohoku region of Japan, 72% of the land comprises mountain forest zones. During winter, severe climatic conditions include heavy snowfall. In such an environment, which is considered high in biodiversity, we assumed that aerobic bacteria would be diverse and would possess the ability to degrade polychlorinated biphenyls (PCBs). In this study, 78 environmental samples were collected from the Tohoku region and 56 aerobic PCB-degrading bacterial strains were isolated. They belonged to the genera Achromobacter, Rhodococcus, Pseudomonas, Stenotrophomonas, Comamonas, Pigmentiphaga, Xenophilus, Acinetobacter, and Pandoraea. Previously reported aerobic PCB-degrading bacterial strains isolated in Japan belonged to the same genera, except that the genera Acidovorax and Bacillus were not identified in the present study. In particular, the isolated Comamonas testosteroni strains YAZ2 and YU14-111 had high PCB-degrading abilities. Analysis of the sequences of the YAZ2 and YU14-111 strains showed that the gene structures of the bph operon, which encode enzymes associated with PCB degradation, were the same as those of the Acidovorax sp. KKS102 strain. Moreover, 2,3-biphenyl dioxygenase activity was responsible for the degradation characteristics of all the isolated strains. Overall, this study suggests that aerobic PCB-degrading bacteria are not specifically endemic to the Tohoku region but distributed across Japan.


Author(s):  
Jialei Gong ◽  
Zhongyi Zheng ◽  
Bufan Zheng ◽  
Yongjun Liu ◽  
Ruiwen Hu ◽  
...  

The traditional shallow tillage method makes the soil quality declining, and affects the efficiency of agricultural production. Taking the conventional rotary tillage(12 cm) as the control, Yunyan 87 as the test variety, and the soil type of the test site is paddy soil, we studied the effects of deep tillage(Subsoiling 30 cm) on soil nutrients, arbuscular mycorrhizal fungi (AMF) and tobacco(Nicotiana tabacum L.)growth. The results showed that deep tillage increased the contents of organic carbon, available phosphorus(AP) and available potassium(AK) in 20 ~ 40 cm soil layer. The community of AMF was changed by deep tillage. Glomus, the dominant genus in both group, increased significantly in the soil after deep tillage. The colonization rate of AMF was lower than that of conventional rotary tillage. Deep tillage was beneficial to the growth of tobacco in the middle and late stages. Root growth and nutrient content of tobacco increased. Deep tillage significantly improved the output value of tobacco. It can be seen that deep tillage is conducive to improving soil fertility, promoting the vigorous growth of root, reducing the dependence of tobacco on AMF, and promoting the high quality and yield of tobacco in drylands of Hunan.


Author(s):  
Jie Yang ◽  
Jie Zhao ◽  
Bobo Wang ◽  
Zhisheng Yu

Anaerobic cellulolytic microbes in gastrointestinal tract (GT) of ruminants have been well-documented, however, knowledge of aerobic microbes with cellulolytic activities in ruminant GT is comparably limited. Here, we unraveled aerobic cultivable cellulolytic microbes in GT of Ujimqin sheep (Ovis aries) and evaluated the cellulolytic potential of promising isolates. Twenty-two strains were found to possess cellulose degrading potential by Congo-red staining and phylogenetic analysis of the 16S rDNA/ITS sequence revealed that all strains belonged to nine genera, i.e., Bacillus, Streptomyces, Pseudomonas, Lactobacillus, Brachybacterium, Sanguibacter, Rhizobium, Fusarium, and Aspergillus. Strains with high cellulolytic activities were selected to further evaluate the various enzyme activities on lignocellulosic alfalfa hay (Medicago sativa). Among them, isolate Bacillus subtilis RE2510 showed the highest potential of cellulose degradation considering the high endoglucanase (0.1478 ± 0.0014 IU ml-1), exoglucanase (0.1735 ± 0.0012 IU ml-1) and β-glucosidase (0.3817 ± 0.0031 IU ml-1) after 10-day incubation with alfalfa hay. A significant destruction effect of the cellulose structure and the attachment of B. subtilis RE2510 to the hay were also revealed by using scanning electron microscope. This study expands our knowledge of aerobic cellulolytic isolates from GT of sheep and also highlights their potential application as microbial additive in the aerobic process of cellulose bioconversion.


Author(s):  
MacLean Glen Kohlmeier ◽  
Harry Yudistira ◽  
Amanat Ali ◽  
Ivan John Oresnik

Bacteriocins are narrow spectrum antibiotics of bacterial origin that can affect competition in resource-limited environments such as the rhizosphere. Therefore, bacteriocins may be good candidates for manipulation in order to generate more competitive inocula for soybean. In this study,<i> B. japonicum</i> FN1 along with other Bradyrhizobia in our culture collection were screened for bacteriocin-like activity. A total of five distinct inhibitory activities could be observed. FN1 genes putatively involved in bacteriocin production were computationally identified. These genes were mutagenized and the subsequent strains were screened for loss of inhibitory activity. Mutant strain BRJ-48, with an insert in<i> bjfn1_01204</i>, displayed a loss of the ability to inhibit an indicator strain. This loss could be complemented by the introduction of a plasmid expressing <i>bjfn1_01204 </i>in trans. The strain carrying the mutation did not affect competition in broth cultures, but was shown to be less competitive for nodule occupancy. Annotation suggests that <i>bjfn1_01204</i> encodes a carboxymuconolactone decarboxylase, however the direct contribution of how this enzyme contributes to inhibiting the tester strain remains unknown.


Author(s):  
Hongrui Zhang ◽  
Weiwei Chen ◽  
Xinyi Wang ◽  
Yongquan Li ◽  
Zhenhong Zhu

The purpose of this study is to explore the function of MarR-family regulator slnO. In addition, the high-yield strain of salinomycin was constructed by using combined regulation strategies. Firstly the slnO gene over-expression strain (GO) was constructed in Streptomyces albus. Compared to wild type (WT) strain,salinomycin production in GO strain was increased about 28%. Electrophoretic mobility gel shift assays (EMSAs) confirmed that SlnO protein can bind specifically to the intergenic region of slnN-slnO, slnQ-slnA1 and slnF-slnT. qRT-PCR experiments also showed that slnA1, slnF, and slnT1 were significantly up-regulated, while the expression level of the slnN gene was down-regulated in GO strain. Secondly, slnN gene deletion strain (slnNDM) was used as the starting strain, and the pathway specific gene slnR in salinomycin gene cluster was over expressed in slnNDM. The new strain was named ZJUS01. The yield of salinomycin in ZJUS01 strain was 25% and 56% higher than that in slnNDM strain and WT strain. Above results indicate that the slnO gene has a positive regulation effect on the biosynthesis of salinomycin. Meanwhile, the yield of salinomycin could be greatly increased by manipulating multiple transcriptional regulations.


Author(s):  
yaqiu Zhang ◽  
Yiqing Deng ◽  
Juan Feng ◽  
Jianmei Hu ◽  
Haoxiang Chen ◽  
...  

In this study, an in-frame deletion of the luxS gene was constructed to reveal the role of LuxS in the physiology and virulence of V. harveyi. The statistical analysis showed no significant differences in the growth ability, biofilm formation, antibiotic susceptibility, virulence by intraperitoneal injection, and the ability of V. harveyi to colonize the spleen and liver of the pearl gentian grouper between the wild-type (WT) and the luxS mutant. However, the deletion of luxS decreased the secretion of extracellular protease, while increased the ability of swimming and swarming. Simultaneously, a luxS-deleted mutant showed overproduction of lateral flagella, and an intact luxS complemented the defect. Since motility is flagella dependent, 16 of V. harveyi flagella biogenesis related genes were selected for further analysis. Based on quantitative real-time reverse transcription-PCR (qRT-PCR), the expression levels of these genes, including the polar flagella genes flaB, flhA, flhF, flhB, flhF, fliS, and flrA and the lateral flagella genes flgA, flgB, fliE, fliF, lafA, lafK, and motY, were significantly up-regulated in the ΔluxS: pMMB207 (ΔluxS+) strain as compared with the V. harveyi 345: pMMB207 (WT+) and C-ΔluxS strains during the early, mid-exponential, and stationary growth phase.


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