Bacterial direct-fed microbials fail to reduce methane emissions in primiparous lactating dairy cows

Direct-fed microbials(DFM) are considered as a promising technique to improve animal productivity without affecting animal health or harming the environment.The potential of three bacterial DFM to reduce methane(CH4)emissions,modulate ruminal fermentation,milk production and composition of primiparous dairy cows was examined in this study.As previous reports have shown that DFM respond differently to different diets,two contrasting diets were used in this study.Eight lactating primiparous cows were randomly divided into two groups that were fed a corn silage-based,high-starch diet(HSD) or a grass silage-based,high-fiber diet(HFD).Cows in each dietary group were randomly assigned to four treatments in a 4 × 4 Latin square design.The bacterial DFM used were selected for their proven CH4-reducing effect in vitro.Treatments included control(without DFM) and 3 DFM treatments: Propionibacterium freudenreichii 53-W(2.9 × 10^10 colony forming units(CFU)/cow per day),Lactobacillus pentosus D31(3.6 × 10^11 CFU/cow per day) and Lactobacillus bulgaricus D1(4.6 × 10^10 CFU/cow per day).Each experimental period included 4 weeks of treatment and 1 week of wash-out,with measures performed in the fourth week of the treatment period.Enteric CH4 emissions were measured during 3 consecutive days using respiration chambers.Rumen samples were collected for ruminal fermentation parameters and quantitative microbial analyses.Milk samples were collected for composition analysis.Body weight of cows were recorded at the end of each treatment period.Irrespective of diet,no mitigating effect of DFM was observed on CH4 emissions in dairy cows.In contrast,Propionibacterium increased CH4 intensity by 27%(g CH4/kg milk) in cows fed HSD.There was no effect of DFM on other fermentation parameters and on bacterial,archaeal and protozoal numbers.Similarly,the effect of DFM on milk fatty acid composition was negligible.Propionibacterium and L.pentosus DFM tended to increase body weight gain with HSD.We conclude that,contrary to the effect previously observed in vitro,bacterial DFM Propionibacterium freudenreichii 53-W,Lactobacillus pentosus D31 and Lactobacillus bulgaricus D1 did not alter ruminal fermentation and failed to reduce CH4 emissions in lactating primiparous cows fed high-starch or high-fiber diets.

Prospective use of bacteriocinogenic Pediococcus pentosaceus as direct-fed microbial having methane reducing potential

Direct-fed microbials（DFM）, generally regarded as safe status, are successfully used in improving rumen ecology, gastro-intestinal health, feed efficiency, milk production and growth rate in ruminants. On the other hand, methanogenesis in rumen, which accounts for a significant loss of ruminant energy and increased greenhouse gas in environment, is of great concern, therefore, use of DFM for improving productivity without compromising the animal health and ecological sustainability is encouraged. The present study was conducted to investigate the methane reducing potential of bacteriocinogenic strain Pediococcus pentosaceus-34. Since, the culture showed no hemolysis on blood agar and DNase activity, hence, it was considered to be avirulent in nature, a prerequisite for any DFM. The culture also showed tolerance to pH 5.0 for 24 h with 0.5% organic acid mixture, whereas when given a shock for 2 h at different p H and organic acids concentrations, it showed growth at pH 3.0 and 4.0 with 0.1 and 1.0% organic acids, respectively, as having good animal probiotics attributes. The total gas production was significantly（P〈0.05） higher in live pedicoccal culture（LPC） and dead pedicoccal culture（DPC） both with wheat straw, when compared to the control. In sugarcane bagasse, gas production was significantly lower（P〈0.05） with LPC compared to the control and DPC both. Methane was reduced by the inclusion of LPC in sugarcane bagasse（0.07 mL CH4 mg–1 dry matter digestibility） with no effect on other rumen fermentation parameters. However, with wheat straw and LPC total gas, in vitro dry matter digestibility, total volatile fatty acids increased significantly but no reduction in methane production was observed in comparison to the control. Therefore, further research is warranted in this direction, if the bacteriocinogenic strains can be used as DFM for ruminants to improve the ruminant productivity.

Implication and challenges of direct-fed microbial supplementation to improve ruminant production and health

Direct-fed microbials(DFMs)are feed additives containing live naturally existing microbes that can benefit animals’health and production performance.Due to the banned or strictly limited prophylactic and growth promoting usage of antibiotics,DFMs have been considered as one of antimicrobial alternatives in livestock industry.Microorganisms used as DFMs for ruminants usually consist of bacteria including lactic acid producing bacteria,lactic acid utilizing bacteria and other bacterial groups,and fungi containing Saccharomyces and Aspergillus.To date,the available DFMs for ruminants have been largely based on their effects on improving the feed efficiency and ruminant productivity through enhancing the rumen function such as stabilizing ruminal pH,promoting ruminal fermentation and feed digestion.Recent research has shown emerging evidence that the DFMs may improve performance and health in young ruminants,however,these positive outcomes were not consistent among studies and the modes of action have not been clearly defined.This review summarizes the DFM studies conducted in ruminants in the last decade,aiming to provide the new knowledge on DFM supplementation strategies for various ruminant production stages,and to identify what are the potential barriers and challenges for current ruminant industry to adopt the DFMs.Overall literature research indicates that DFMs have the potential to mitigate ruminal acidosis,improve immune response and gut health,increase productivity(growth and milk production),and reduce methane emissions or fecal shedding of pathogens.More research is needed to explore the mode of action of specific DFMs in the gut of ruminants,and the optimal supplementation strategies to promote the development and efficiency of DFM products for ruminants.

Control Effect of Different Microbial Agents on Tobacco Bacterial Wilt

[ Objectives] The paper was to study effects of different microbial agents on occurrence of tobacco bacterial wilt. [ Methods I Antagonistic strains against Ralstonia solanacearum were screened from in situ soil, and prepared into four different combinations. The number of soil microorganisms and incidence of bacterial wilt of four combinations were observed. [ Results] The incidence rate of bacterial wilt treated by microbial agent OR-1 was significantly lower than that in control, and the control efficacy against bacterial wilt reached 67%. [ Conclusions] Application of microbial agent OR-1 could effectively reduce the incidence rate and disease index of bacterial wilt, thus improving the quality of tobacco.

Isolation, screening and identifi cation of Bacillus spp. as direct-fed microbial candidates for aflatoxin B_1 biodegradation

Objective: To evaluate the ability of Bacillus spp. as direct-fed microbials(DFM) to biodegrade al atoxin B1(AFB1) by using an in vitro digestive model simulating in vivo conditions.Methods: Sixty-nine Bacillus isolates were obtained from intestines, and soil samples were screened by using a selective media method against 0.25 and 1.00 μg/m L of AFB1 in modii ed Czapek-Dox medium. Plates were incubated at 37 °C and observed every two days for two weeks. Physiological properties of the three Bacillus spp. candidates were characterized biochemically and by 16 S r RNA sequence analyzes for identii cation. Tolerance to acidic p H, osmotic concentrations of Na Cl, bile salts were tested, and antimicrobial sensitivity proi les were also determined. Bacillus candidates were individually sporulated by using a solid fermentation method and combined. Spores were incorporated into 1 of 3 experimental feed groups: 1) Negative control group, with unmedicated starter broiler feed without AFB1; 2) Positive control group, with negative control feed contaminated with 0.01% AFB1; 3) DFM treated group, with positive control feed supplemented with 109 spores/g. After digestion time(3:15 h), supernatants and digesta were collected for high-performance liquid chromatography l uorescence detection analysis by triplicate.Results: Three out of those sixty-nine DFM candidates showed ability to biodegrade AFB1 in vitro based on growth as well as reduction of l uorescence and area of clearance around each colony in modii ed Czapek-Dox medium which was clearly visible under day light after 48 h of evaluation. Analysis of 16S-DNA identii ed the strains as Bacillus amyloliquefaciens, Bacillus megaterium and Bacillus subtilis. The three Bacillus strains were tolerant to acidic conditions(p H 2.0), tolerant to a high osmotic pressure(Na Cl at 6.5%), and were able to tolerate 0.037% bile salts after 24 h of incubation. No signii cant dif erences(P > 0.05) were observed in the concentrations of AFB1 in neither the supernatants nor digesta samples evaluated by highperformance liquid chromatography with l uorescence detection between positive control or DFM treated groups. Conclusions: In vitro digestion time was not enough to confirm biodegradation of AFB1. Further studies to evaluate the possible biodegradation ef ects of the BacillusDFM when continuously administered in experimentally contaminated feed with AFB1, are in progress.

Response of microbial biomass and bacterial community composition to fertilization in a salt marsh in China

The effects of nitrogen （N） addition on microbial biomass, bacterial abundance, and community composition in sediment colonized by Suaeda heteroptera were examined by chloroform fumigation extraction method, real-time quantitative polymerase chain reaction, and denaturing gradient gel electrophoresis （DGGE） in a salt marsh located in Shuangtai Estuary, China. The sediment samples were collected from plots treated with different amounts of a single N fertilizer （urea supplied at 0.1, 0.2, 0.4 and 0.8 g/kg （nitrogen content in sediment） and different forms of N fertilizers （urea, （NH4）2SO4, and NH4NO3, each supplied at 0.2 g/kg （calculated by nitrogen）. The fertilizers were applied 1-4 times during the plant-growing season in May, luly, August, and September of 2013. Untreated plots were included as a control. The results showed that both the amount and form of N positively influenced microbial biomass carbon, microbial biomass nitrogen, and bacterial abundance. The DGGE profiles revealed that the bacterial community composition was also affected by the amount and form of N. Thus, our findings indicate that short-term N amendment increases microbial biomass and bacterial abundance, and alters the structure of bacterial community.

Effects of Bio-organic Fertilizer with Antagonistic Bacteria against Tobacco Bacterial Wilt on Soil Microbial Communities and Disease Resistance of Tobacco

In this study, the effects of bio-organic fertilizer with antagonistic bacteria against tobacco bacterial wilt on soil microbial communities and disease resist- ance of tobacco were investigated by field experiment. The results showed that the incidence of tobacco bacterial wilt in bio-organic fertilizer treatments （T3 and T4） decreased remarkably among four treatments in the field. Compared with the local conventional fertilization group, the incidence of tobacco bacterial wilt was re- duced by 21.9% and 25.0% in T3 and T4, respectively ; the yield of flue-cured tobacco was improved by 5.7% and 5.3%, respectively ; the proportion of mid- high grade tobacco leaves increased by 2.3% and 2.6%, respectively. After application of bio-organie fertilizer with antagonistic bacteria against tobacco bacterial wilt, rhizosphere soil microbial communities exhibited vast amount and abundant species ; the amount of rhizosphere soil bacteria of infected tobacco plants was im- proved by 218.5% with fewer species. It could be concluded that the application of bio-organic fertilizer with antagonistic bacteria against tobacco bacterial wilt could improve the ecological environment of tobacco field, inhibit the growth of pathogenic bacteria, decrease the incidence of tobacco bacterial wilt, and enhance the quality of flue-cured tobacco. This study laid the foundation for further ecological prevention and control of soil-borne diseases of tobacco.

Effect of Direct-Fed Microbial Supplementation on Pathogenic <i>Escherichia coli</i>Fecal Shedding, Live Performance, and Carcass Characteristics in Feedlot Steers

Three experiments were conducted to evaluate direct-fed microbial (DFM) supplementation on live performance, carcass characteristics, and fecal shedding of E. coli in feedlot steers. In Exp. 1, 400 steers (BW = 348 kg) were assigned to treatments: CON = lactose carrier only, BOV = P. freudenreichii (NP24) + L. acidophilus (NP51), BOVD = P. freudenreichii (NP24) + L. acidophilus (NP51), and COMB = BOV fed for the first 101 d on feed, followed by BOVD for the final 28 d prior to harvest. In Exp. 2 (n = 1800;BW = 354 kg) and Exp. 3 (n = 112;BW = 397 kg), steers were utilized in a randomized complete block design and assigned to DFM treatments using low dose and high dose, respectively. Fecal samples were collected prior to harvest and analyzed for E. coli serogroups. In Exp. 1, DFM reduced (P < 0.01) the concentration of E. coli O157. Prevalence of O157 was reduced by BOVD supplementation in Exp. 2 and 3 (P < 0.01 and P = 0.08, respectively), and concentration of E. coli O157 in positive samples was reduced in both experiments where enumeration was performed (P ≤ 0.02). Weighted mean differences across the three experiments were equal to a 33% reduction in the prevalence of E. coli O157:H7 in BOVD treated cattle. A significant reduction in prevalence of O26, O45, O103, and O121 was observed in Exp. 2 (P ≤ 0.03). These results indicate that high levels of L. acidophilus (NP51) may represent an effective pre-harvest food safety intervention to reduce fecal shedding of several E. coli serogroups.

Recent progress in microbial cell surface display systems and their application on biosensors

Microbial cell surface display technology is a recombinant technology to express target proteins on the cell membrane,which can be used to redesign the cell surface with functional proteins and peptides.Bacterial and yeast surface display systems are the most common cell surface display systems of prokaryotic and eukaryotic proteins,that are widely applied as the core elements in the field of biosensors due to their advantages,including enhanced stability,high yield,good safety,expression of larger and more complex proteins.To further promote the performance of biosensors,the biomineralized microbial surface display technology was proposed.This review summarized the different microbial surface display systems and the biomineralized surface display systems,where the mechanisms of surface display and biomineralization were introduced.Then we described the recent progress of their applications on biosensors for different types of detection targets.Finally,the outlooks and tendencies were discussed and forecasted with the expectation to provide some general functions and enlightenments to this aspect of research.

Effects of maize-soybean relay intercropping on crop nutrient uptake and soil bacterial community

Maize-soybean relay intercropping is an effective approach to improve the crop yield and nutrient use efficiency,which is widely practiced by farmers in southwest of China.To elucidate the characteristics of different planting patterns on crop nutrient uptake,soil chemical properties,and soil bacteria community in maize-soybean relay intercropping systems,we conducted a field experiment in 2015–2016 with single factor treatments,including monoculture maize(MM),monoculture soybean(MS),maize-soybean relay intercropping(IMS),and fallow(CK).The results showed that the N uptake of maize grain increased in IMS compared with MM.Compared with MS,the yield and uptake of N,P,and K of soybean grain were increased by 25.5,24.4,9.6,and 22.4%in IMS,respectively,while the N and K uptakes in soybean straw were decreased in IMS.The soil total nitrogen,available phosphorus,and soil organic matter contents were significantly higher in IMS than those of the corresponding monocultures and CK.Moreover,the soil protease,soil urease,and soil nitrate reductase activities in IMS were higher than those of the corresponding monocultures and CK.The phyla Proteobacteria,Acidobacteria,Chloroflexi,and Actinobacteria dominated in all treatments.Shannon’s index in IMS was higher than that of the corresponding monocultures and CK.The phylum Proteobacteria proportion was positively correlated with maize soil organic matter and soybean soil total nitrogen content,respectively.These results indicated that the belowground interactions increased the crop nutrient(N and P)uptake and soil bacterial community diversity,both of which contributed to improved soil nutrient management for legume-cereal relay intercropping systems.

Dynamic changes in microbial activity and community structure during biodegradation of petroleum compounds:A laboratory experiment

With 110-d incubation experiment in laboratory, the responses of microbial quantity, soil enzymatic activity, and bacterial community structure to different amounts of diesel fuel amendments were studied to reveal whether certain biological and biochemical characteristics could serve as reliable indicators of petroleum hydrocarbon contamination in meadow-brown soil, and use these indicators to evaluate the actual ecological impacts of 50-year petroleum-refining wastewater irrigation on soil function in Shenfu irrigation area. Results showed that amendments of ~ 1000 mg/kg diesel fuel stimulated the growth of aerobic heterotrophic bacteria, and increased the activity of soil dehydrogenase, hydrogenperoxidase, polyphenol oxidase and substrate-induced respiration. Soil bacterial diversity decreased slightly during the first 15 d of incubation and recovered to the control level on day 30. The significant decrease of the colony forming units of soil actinomyces and filamentous fungi can be taken as the sensitive biological indicators of petroleum contamination when soil was amended with 〉15000 mg/kg diesel fuel. The sharp decrease in urease activity was recommended as the most sensitive biochemical indicator of heavy diesel fuel contamination. The shifts in community structure to a community documented by Sphingomonadaceae within a-subgroup of Proteobacteria could be served as a sensitive and precise indicator of diesel fuel contamination. Based on the results described in this paper, the soil function in Shenfu irrigation area was disturbed to some extent.

Role of live microbial feed supplements with reference to anaerobic fungi in ruminant productivity: A review

To keep the concept of a safe food supply to the consumers, animal feed industries world over are showing an increasing interest in the direct-fed microbials（DFM） for improved animal performance in terms of growth or productivity. This becomes all the more essential in a situation, where a number of the residues of antibiotics and/or other growth stimulants reach in milk and meat with a number of associated potential risks for the consumers. Hence, in the absence of growth stimulants, a positive manipulation of the rumen microbial ecosystem to enhance the feedstuff utilization for improved production efficiency by ruminants has become of much interest to the researchers and entrepreneurs. A few genera of live microbes（i.e., bacteria, fungi and yeasts in different types of formulations from paste to powder） are infrequently used as DFM for the domestic ruminants. These DFM products are live microbial feed supplements containing naturally occurring microbes in the rumen. Among different DFM possibilities, anaerobic rumen fungi（ARF） based additives have been found to improve ruminant productivity consistently during feeding trials. Administration of ARF during the few trials conducted, led to the increased weight gain, milk production, and total tract digestibility of feed components in ruminants. Anaerobic fungi in the rumen display very strong cell-wall degrading cellulolytic and xylanolytic activities through rhizoid development, resulting in the physical disruption of feed structure paving the way for bacterial action. Significant improvements in the fiber digestibility were found to coincide with increases in ARF in the rumen indicating their role. Most of the researches based on DFM have indicated a positive response in nutrient digestion and methane reducing potential during in vivo and/or in vitro supplementation of ARF as DFM. Therefore, DFM especially ARF will gain popularity but it is necessary that all the strains are thoroughly studied for their beneficial properties to have a confirmed ‘generally regarded as safe＇ status for ruminants.

Alteration of microbial properties and community structure in soils exposed to napropamide

The effect of pesticide napropamide （N,N-diethyl-2-（1-naphthalenyloxy） propanamide） on soil microorganisms for long-term （56 d） was assessed by monitoring changes in soil microbial biological responses. Soils were treated with napropamide at 0, 2, 10, 20, 40, and 80 mg/kg soil and sampled at intervals of 1, 3, 7, 14, 28, 42, and 56 d. The average microbial biomass C declined in napropamide-treated soils as compared to control. The same trend was observed on microbial biomass N after napropamide application. We also determined the basal soil respiration （BSR） and observed a high level in soils treated with napropamide during the first 7 d of experiment. But with the passage of incubation time, BSR with napropamide decreased relatively to control. Application of napropamide at 2-80 mg/kg soil had inhibitory effects on the activity of urease and invertase. Activity of catalase was enhanced during the initial 7 d of napropamide application, but soon recovered to the basal level. The depressed enzyme activities might be due to the toxicity of napropamide to the soil microbial populations. To further understand the effect of napropamide on microbial communities, a PCR- DGGE-based experiment and cluster analysis of 16S rDNA community profiles were performed. Our analysis revealed an apparent difference in bacterial-community composition between the napropamide treatments and control. Addition of napropamide apparently increased the number of bands during the 7-14 d of incubation. These results imply that napropamide-induced toxicity was responsible for the disturbance of the microbial populations in soil.

Soil fungistasis and its relations to soil microbial composition and diversity:A case study of a series of soils with different fungistasis

Fungistasis is one of the important approaches to control soil-borne plant pathogens.Some hypotheses about the mechanisms for soil fungistasis had been established,which mainly focused on the soil bacterial community composition,structure,diversity as well as function.In this study,the bacterial community composition and diversity of a series of soils treated by autoclaving,which coming from the same original soil sample and showing gradient fungistasis to the target soil-borne pathogen fungi Fusarium grami...

Effects of viral infection and microbial diversity on patients with sepsis:A retrospective study based on metagenomic next-generation sequencing

BACKGROUND: The study aims to investigate the performance of a metagenomic next-generationsequencing (NGS)-based diagnostic technique for the identifi cation of potential bacterial and viral infectionsand eff ects of concomitant viral infection on the survival rate of intensive care unit (ICU) sepsis patients.METHODS: A total of 74 ICU patients with sepsis who were admitted to our institution from February1, 2018 to June 30, 2019 were enrolled. Separate blood samples were collected from patients for bloodcultures and metagenomic NGS when the patients’ body temperature was higher than 38 °C. Patients’demographic data, including gender, age, ICU duration, ICU scores, and laboratory results, were recorded.The correlations between pathogen types and sepsis severity and survival rate were evaluated.RESULTS: NGS produced higher positive results (105 of 118;88.98%) than blood cultures(18 of 118;15.25%) over the whole study period. Concomitant viral infection correlated closelywith sepsis severity and had the negative effect on the survival of patients with sepsis. However,correlation analysis indicated that the bacterial variety did not correlate with the severity of sepsis.CONCLUSIONS: Concurrent viral load correlates closely with the severity of sepsis and thesurvival rate of the ICU sepsis patients. This suggests that prophylactic administration of antiviraldrugs combined with antibiotics may be benefi cial to ICU sepsis patients.

Seasonal Development of Microbial Activity in Soils of Northern Norway

Seasonal development of soil microbial activity and bacterial biomass in sub-polar regions was investigated to determine the impacts of biotic and abiotic factors, such as organic matter content, temperature and moisture. The study was performed during spring thaw from three cultivated meadows and two non-cultivated forest sites near Alta, in northern Norway. Samples from all five sites showed increasing respiration rates directly after the spring thaw with soil respiration activity best related to soil organic matter content. However, distributions of bacteria] biomass showed fewer similarities to these two parameters. This could be explained by variations of litter exploitation through the biomass. Microbial activity started immediately after the thaw while root growth had a longer time lag. An influence of root development on soil microbes was proposed for sites where microorganisms and roots had a tight relationship caused by a more intensive root structure. Also a reduction of microbial activity due to soil compaction in the samples from a wheel track could not be observed under laboratory conditions. New methodological approaches of differential staining for live and dead organisms were applied in order to follow changes within the microbial community. Under laboratory conditions freeze and thaw cycles showed a damaging influence on parts of the soil bacteria. Additionally, different patterns for active vs. non-active bacteria were noticeable after freeze-thaw cycles.

Direct-fed microbes: A tool for improving the utilization of low quality roughages in ruminants

For many years, ruminant nutritionists and microbiologists have been interested in manipulating the microbial ecosystem of the rumen to improve production efficiency of different ruminant species. Removal and restriction of antibiotics subtherapeutic uses from ruminant diets has amplified interest in improving nutrient utilization and animal performance and search for more safe alternatives. Some bacterial and fungal microorganisms as a direct-fed microbial（DFM） can be the most suitable solutions. Microorganisms that are commonly used in DFM for ruminants may be classified mainly as lactic acid producing bacteria（LAB）, lactic acid utilizing bacteria（LUB）, or other microorganism＇s species like Lactobacillus, Bifidobacterium, Enterococcus, Streptococcus, Bacillus, Propionibacterium, Megasphaera elsdenii and Prevotellabryantii, in addition to some fungal species of yeast such as Saccharomyces and Aspergillus. A definitive mode of action for bacterial or fungal DFM has not been established; although a variety of mechanisms have been suggested. Bacterial DFM potentially moderate rumen conditions, and improve weight gain and feed efficiency. Fungal DFM may reduce harmful oxygen from the rumen, prevent excess lactate production, increase feed digestibility, and alter rumen fermentation patterns. DFM may also compete with and inhibit the growth of pathogens, immune system modulation, and modulate microbial balance in the gastrointestinal tract. Improved dry matter intake, milk yield, fat corrected milk yield and milk fat content were obtained with DFM administration. However, the response to DFM is not constant; depending on dosages, feeding times and frequencies, and strains of DFM. Nonetheless, recent studies have supported the positive effects of DFM on ruminant performance.

Effect of Yeast Culture and Direct-Fed Microbes on the Growth Performance and Rumen Fermentation of Weaner Lambs

The effects of yeast culture and directfed microbes on the growth performance of weaner lambs was examined. Thirty-two Hu lambs with inihtial weight of 22.20 （ ±0.75 ） kg were randomly assigned to one of four treatments： basal diet without additive （control）, added with yeast culture at 15 g/head/d （YEC）, YEC plus Bacillus licheniformis preparation at 2. 3 g/head/d （YBL） or plus Clostridium butyricum preparation at 2. 3 g/head/d （YCB）. The feeding trial lasted 75 d with 15 d for adaptation. Feed intake was not influenced （P 〉0. 05） by treatment. Average daily gain of growing lambs was 102, 114, 90, and 89 g/d in control, YEC, YBL, and YCB, respectively, with no significant difference （P 〉 0.05） among treatments, but the carcass weight of YEC lambs was significantly higher （P 〈 0.05） than that of other treatments. Total volatile fatty acids and acetate to propionate ratio in the rumen were unaffected, although the butyric acid concentration was higher （ P 〈 0.05 ） in the ru men fluid of YCB lambs compared with YEC lambs and slightly higher （ P 〉 0. 05 ） than in controls and YBL lambs. Solid-associated fungi population relative to total rumen bacteria 16S ribosomal DNA was significantly lower （ P 〈 0. 05 ） in YBL lambs （3.55） compared with those on YCB （23.12）. There was little difference in blood glucose and plasma urea-N concentrations among the treatments. Blood concentrations of creatinine and globulin were significantly higher （P 〈0.05） in YBL lambs, compared with the control and YEC-fed animals, and no difference with YCB lambs. Total protein and triglycerides in blood were significantly （P 〈 0.05） higher in YBL lambs, compared with controls. These serum biochemical parameters suggest that treatment increased amounts of absorbable protein but not efficiency of protein utilization and in YBL and YCB lambs. The results indicated that yeast culture improve growth performance, while little advantage could be expected from combining yeast culture with either the B. licheniformis preparation or C. butyricum preparation. More research using lower doses of B. licheniformis prepara- tion or C. butyricum preparation in combination with yeast culture is warranted.

Changes in bacterial community and abundance of functional genes in paddy soil with cry1Ab transgenic rice

A field experiment involving cry1Ab transgenic rice(GM) and its parental non-cry1Ab rice(M) has been on-going since 2014. The diversity of the bacterial communities and the abundance of the microbial functional genes which drive the conversion of nitrogen in paddy soil were analyzed during the growth period of rice in the fifth year of the experiment, using 16 S rRNAbased Illumina Mi Seq and real-time PCR on the amoA, nirS and nirK genes. The results showed no differences in the alpha diversity indexes of the bacterial communities, including Chao1, Shannon and Simpson, between the fields cultivated with line GM and cultivar M at any of the growth stages of rice. However, the bacterial communities in the paddy soil with line GM were separated from those of paddy soil with cultivar M at each of the growth stages of rice, based on the unweighted Uni Frac NMDS or PCoA. In addition, the analyses of ADONIS and ANOSIM, based on the unweighted Uni Frac distance, indicated that the above separations between line GM and cultivar M were statistically significant(P<0.05) during the growth season of rice. The increases in the relative abundances of Acidobacteria or Bacteroidetes, in the paddy soils with line GM or cultivar M, respectively, led to the differences in the bacterial communities between them. At the same time, functional gene prediction based on Illumina Mi Seq data suggested that the abundance of many functional genes increased in the paddy soil with line GM at the maturity stage of rice, such as genes related to the metabolism of starch, amino acids and nitrogen. Otherwise, the copies of bacterial amo A gene, archaeal amo A gene and denitrifying bacterial nir K gene significantly increased(P<0.05 or 0.01) in the paddy soil with line GM. In summary, the release of cry1Ab transgenic rice had effects on either the composition of bacterial communities or the abundance of microbial functional genes in the paddy soil.

Sediment bacterial communities are more complex in coastal shallow straits than in oceanic deep straits

Straits are ideal models to investigate the bacterial community assembly in complex hydrological environments. However, few studies have focused on bacterial communities in them. Here, comparable bacterial communities in costal shallow Bohai Strait(BS) and oceanic deep Fram Strait(FS) were studied. The Shannon and Chao1 indices were both higher in BS than in FS. The relative abundances of the classes Deltaproteobacteria and Bacilli and the family Halieaceae were higher in BS than in FS, in contrast to the families OM1_clade and JTB255_marine_benthic_group, revealing typical characteristics of bacterial communities in coastal and oceanic regions. Cluster analysis based on the Bray-Curtis index showed that samples were clustered by depth layer in FS and BS, indicating that structures of bacterial communities would diff er with increasing water depth in straits. Additionally, the cluster relationships among samples in abundant and rare communities were both similar to those in entire communities. However, the dissimilarities among samples showed a descending order as rare communities, entire communities and abundant communities. Network analysis indicated that the BS network was obviously more complex than the FS network. Filamentous bacteria Desulfobulbaceae exhibited high degree values in BS but not in FS, indicating key roles of Desulfobulbaceae in the BS. Our study provides different and common evidences for understanding microbial ecology in coastal shallow and oceanic deep straits.