Changes in Bacterial Populations in Aquatic Environment of Carassius auratus gibelio during an Outbreak of Diseases

During an outbreak of diseases caused by co-infection with both parasites and bacteria in silver crucian carp （ Carassius auratus gibelio）, aerobic anoxy- genic phototrophic （AAP） bacteria in the aquatic environment were identified by PCR using the universal primers of bacterial 16S rDNA. The bacterial populations in the ponds infected and non-infected by the diseases were measured with acridine orange direct count （AODC） method, and the data were analyzed using SPSS software. The results showed that nine dominant cuhurable bacterial species： Shewanella putrefaciens, Acinetobacter sp. , Aeromonas sp. , Proteus vulgaris, Xan- thomonas sp. , Citrobacterfieundii, Morganella morganii, Vagococcus lutrae and Providencia sp. were identified, some of which were common pathogens. The bac- terial population in infected ponds was 7. 462 x 10^6 ind./ml in July, and 1. 007 4 x 10^7 ind./ml in August, and that in non-infected ponds was 1. 460 x 10x6ind./ml in July, and 1. 911 x10^6 ind./ml in August, with significant differences between the infected and non-infected ponds. The results suggested that the outbreak of diseases in silver crucian carp was to some extent related to the bacterial population in water environment.

Partially replacing cornstarch in a high-concentrate diet with sucrose inhibited the ruminal trans-10 biohydrogenation pathway in vitro by changing populations of specific bacteria

Background： The positive influence of replacing dietary starch with sugar on milk fat production has been proposed to be partially attributed to the inhibition of the rumen trans-10 biohydrogenation pathway. However,whether and how sucrose inhibits the rumen trans-10 biohydrogenation pathway remains elusive.Results： A batch in vitro incubation system was used to evaluate effects of replacing cornstarch in a high-concentrate diet（forage to concentrate ratio = 40：60） with 0（control）, 3, 6 and 9 % of sucrose on rumen fermentation pattern, fatty acid（FA） biohydrogenation pathways and bacterial populations relating to trans-11 to trans-10 biohydrogenation pathways. Replacing dietary cornstarch with sucrose did not alter rumen p H or concentrations of total volatile fatty acids（VFA） in comparison with the control but significantly influenced the profiles of individual VFA. The molar proportions of butyrate and valerate were linearly increased, while that of acetate was quadratically decreased and those of propionate, isobutyrate and isovalerate were linearly decreased with increasing concentrations of sucrose in the diet. Furthermore, replacing cornstarch with sucrose led to a linear decrease in C18：1 trans-10, linear increases in the proportions of C18：1 trans-11, C18：2n-6 and the ratio of trans-11 to trans-10, and linear decreases in biohydrogenation of C18：2n-6 and C18：3n-3. The abundance of Butyrivibrio fibrisolvens, a butyrate and CLA cis-9,trans-11 producer, was increased with the increasing inclusion of sucrose in the diet, while the population of Megasphaera elsdenii, a CLA trans-10, cis-12 producer, was significantly decreased by all levels of sucrose replacements.Conclusions： These results indicate that replacing starch in a high-concentrate diet with sucrose increased butyrate production and inhibited the rumen trans-10 biohydrogenation pathway, which was at least partially due to increased abundance of Butyrivibrio fibrisolvens and decreased abundance of Megasphaera elsdenii.

Long-term and combined effects of N-[2-(nitrooxy)ethyl]-3-pyridinecarboxamide and fumaric acid on methane production,rumen fermentation, and lactation performance in dairy goats

Background:In recent years,nitrooxy compounds have been identified as promising inhibitors of methanogenesis in ruminants.However,when animals receive a nitrooxy compound,a high portion of the spared hydrogen is eructated as gas,which partly offsets the energy savings of CH4mitigation.The objective of the present study was to evaluate the long-term and combined effects of supplementation with N-[2-(nitrooxy)ethyl]-3-pyridinecarboxamide(NPD),a methanogenesis inhibitor,and fumaric acid(FUM),a hydrogen sink,on enteric CH4production,rumen fermentation,bacterial populations,apparent nutrient digestibility,and lactation performance of dairy goats.Results:Twenty-four primiparous dairy goats were used in a randomized complete block design with a 2×2factorial arrangement of treatments:supplementation without or with FUM(32 g/d)or NPD(0.5 g/d).All samples were collected every 3 weeks during a 12-week feeding experiment.Both FUM and NPD supplementation persistently inhibited CH4yield(L/kg DMI,by 18.8%and 18.1%,respectively)without negative influence on DMI or apparent nutrient digestibility.When supplemented in combination,no additive CH4suppression was observed.FUM showed greater responses in increasing the molar proportion of propionate when supplemented with NPD than supplemented alone(by 10.2%vs.4.4%).The rumen microbiota structure in the animals receiving FUM was different from that of the other animals,particularly changed the structure of phylum Firmicutes.Daily milk production and serum total antioxidant capacity were improved by NPD,but the contents of milk fat and protein were decreased,probably due to the bioactivity of absorbed NPD on body metabolism.Conclusions:Supplementing NPD and FUM in combination is a promising way to persistently inhibit CH4emissions with a higher rumen propionate proportion.However,the side effects of this nitrooxy compound on animals and its residues in animal products need further evaluation before it can be used as an animal feed additive.

Microbial Community Structure of Casing Soil During Mushroom Growth

The culturable bacterial population and phospholipid fatty acid （PLFA） profile of casing soil were investigated at different mushroom （Agaricus bisporus） cropping stages. The change in soil bacterial PLFAs was always accompanied by a change in the soil eulturable bacterial population in the first flush. Comparatively higher culturable bacterial population and bacterial PLFAs were found in the casing soil at the primordia formation stage of the first flush. There was a significant increase in the ratio of fungal to bacterial PLFAs during mushroom growth. Multivariate analysis of PLFA data demonstrated that the mushroom cropping stage could considerably affect the microbial community structure of the casing soil. The bacterial population increased significantly from casing soil application to the primordia formation stage of the first flush. Casing soil application resulted in an increase in the ratio of gram-negative bacterial PLFAs to gram-positive bacterial PLFAs, suggesting that some gram-negative bacteria might play an important role in mushroom sporophore initiation.

Gram-Positive Bacteria Associated with Rice in China and Their Antagonists Against the Pathogens of Sheath Blight and Bakanae Disease in Rice

It is necessary to understand the bacterial populations associated with rice so as to provide more information and natural resources for effective management of major diseases in rice. A survey on screening and identification of gram-positive bacteria was conducted during 1998 2004. Seven hundred and fifty-six rice samples were collected from Zhejiang, Jiangsu, Fujian and Yunnan Provinces, China. Over 1000 bacterial isolates were isolated and tested for colony morphology, pathogenicity, and some characteristics of bacteriology including Gram staining, fluorescent pigment on Kings medium B and microscopic observation for endospore. Together with five standard reference strains, 74 representative gram-positive bacterial isolates were confirmed by Biolog and gas chromatographic analysis of fatty acid methyl esters. Five bacterial species of Bacillus and other three genera were identified and isolates from Bacillus sublitis and Bacillus megaterium, exhibited the most effective inhibition against the pathogens of sheath blight and bakanae disease of rice. A few isolates from Bacillus pumilus and Bacillus megaterium showed weak virulent on rice together with some virulent isolates, risk should be considered when isolates from these species were screened for biocontrol agents.

Responses of Iron-Reducing Bacteria to Salinity and Organic Matter Amendment in Paddy Soils of Thailand

In paddy soils of Thailand, the addition of organic matter （OM） is used to efficiently limit the effect of salinity on rice culture and production. OM used as an amendment and fertilizer promotes the reduced condition and increases iron solubilization without provoking ferrous toxicity. In this study, the intricate biogeochemical role of iron-reducing bacteria （IRB） involved in the quality of water and soil of paddy fields, particularly when the paddy fields were subject to salinity and organic matter addition, were studied in paddy fields of Thailand. The results demonstrated that the addition of OM increased the proliferation of cultivable IRB and their specific activity. Cultivable IRB communities decreased in the presence of salt. The presence of salt modified the structure of the bacterial populations by favoring the development of alkaline and moderately halophilic bacteria （Virgibacillus spp., Occanobacillus spp., and PaenibaciUus spp.）. The paddy soils studied contained very diversified （halosensitive, halotolerant, and halophilic） IRB populations that could be adapted to a variety of salinity conditions （0-90 g L-1 NaCI） using different organic substrates （glucose, acetate, and soil organic matter） to maintain significant activities under extreme conditions of salinity. The rhizosphere of rice stimulated IRB community growth without organic matter, whereas organic matter addition limited the rhizosphere effect on IRB cultivable number in saline condition. The interactive action of salinity and organic amendment had a negative impact on the rhizosphere effect. The presence of specific iron-reducing populations （fermentative, iron-respiring, anaerobic, and facultative anaerobic）, having different behaviors under salt and redox stresses, appeared to be a key factor that contributed to the control or enhancement of the quality of water and soil in paddy fields.

Characterization of a phenanthrene-degrading methanogenic community

Polycyclic aromatic hydrocarbons(PAHs)often occur in oil-contaminated soil,coke wastewater and domestic sludge;however,associated PAH degraders in these environments are not clear.Here we evaluated phenanthrene degradation potential in the mixed samples of above environments,and obtained a methanogenic community with different microbial profile compared to those from sediments.Phenanthrene was efficiently degraded(1.26 mg/L/d)and nonstoichiometric amount of methane was produced simultaneously.16S rRNA gene sequencing demonstrated that bacterial populations were mainly associated with Comamonadaceae Nocardiaceae and Thermodesulfobiaceae,and that methanogenic archaea groups were dominated by Methanobacterium and Methanothermobacter.Substances such as hexane,hexadecane,benzene and glucose showed the most positive effects on phenanthrene degradation.Substrate utilization tests indicated that this culture could not utilize other PAHs.These analyses could offer us some suggestions on the putative phenanthrene-degrading microbes in such environments,and might help us develop strategies for the removal of PAHs from contaminated soil and sludge.