Diversity of proteolytic community encoding for subtilisin in an arable field: spatial and temporal variability

The diversity of soil proteolytic community encoding for subtilisin (sub) was investigated at a cultivated field site with four different soil types and at three different depths in April, July, and October. A terminal restriction fragment length polymorphism (T-RFLP) analysis of subtilisin gene (sub) was applied to study dynamic of the sub gene pool. The aim of the present study was to relate differences in sub community structure to the vertical, site, and seasonal variations naturally occurring at the field site under investigation. A significant spatial variability in the community structure of sub-containing bacteria was observed. The richness of sub proteolytic bacterial population decreased with increasing soil depth, revealing the highest values in upper layers. A similar trend was observed among the different sites; the highest diversity was noticed at the site with the highest silt and nutrient content. The reasons behind the observed patterns in the community structure might be varying water amount and spatial isolation along the soil profile as well as variability of the quantity and quality of available substrates among different depths and different sites.     

Evaluating of the Association Between Early-stage Weight and Gut Microbiota in Duroc Pigs Using 16S rRNA Sequencing

The purpose of this study was to explore the possible association of the intestinal microbiome with early-stage weight in Duroc pigs.80 days old weaned piglets with Lighter body weight (LBW,n=9) and heavier body weight (HBW,n=9) were selected from 91 individuals based on their body weights ranked.Fecal samples from piglets in the early grower phase were performed for microbial diversity,composition and predicted functionality by sequencing the V3-V4 region of 16S rRNA gene.The results showed that there was no significant differences in microbial Alpha diversity between HBW and LBW groups(P>0.05).The two dominant phyla detected in both groups were Firmicutes (65.62% and 66.57% in HBW and LBW groups) and Bacteroidetes (30.87% and 29.80% in HBW and LBW groups).Four dominant genera were Prevotella (23.82% and 20.84% in HBW and LBW groups),Lactobacillus (9.11% and 16.55% in HBW and LBW groups),norank_f_Ruminococcaceae (10.32% and 9.98% in HBW and LBW groups),and norank_f_Lachnospiraceae (6.33% and 4.53% in HBW and LBW groups).PCoA analysis showed that there were small differences in gut microbes among Duroc piglets,whereas,some weight-associated microbial compositional differences were revealed between HBW and LBW groups.At the genus level,the abundance of several genera,such as g_Kitasatospora,g_norank_o_Tremblayales,g_norank_f_Erysipelotrichaceae,g_unclassified_f_[Paraprevotellaceae] and g_Coprobacillus,were significantly higher in HBW group than in LBW group (P<0.05).The abundance of Corynebacterium in LBW group was significantly higher than that in HBW group (P<0.05).Moreover,the KEGG pathways analysis showed that the sesquiterpenoid biosynthesis,insulin signaling pathway,ascorbate and aldarate metabolism,and biosynthesis of ansamycins were significantly enriched in HBW group (P<0.05),however,the secretion system pathway was significantly enriched in LBW group (P<0.05).These results might provide insights into host-microbe interactions occurring in the early stage piglets and would be useful in contributing to healthy pig breeding.     

Differential responses of total and active soil microbial communities to long-term experimental N deposition

The relationship between total and metabolically active soil microbial communities can provide insight into how these communities are impacted by environmental change, which may impact the flow of energy and cycling of nutrients in the future. For example, the anthropogenic release of biologically available N has dramatically increased over the last 150 years, which can alter the processes controlling C storage in terrestrial ecosystems. In a northern hardwood forest ecosystem located in Michigan, USA, nearly 20 years of experimentally increased atmospheric N deposition has reduced forest floor decay and increased soil C storage. A microbial mechanism underlies this response, as compositional changes in the soil microbial community have been concomitantly documented with these biogeochemical changes. Here, we co-extracted DNA and RNA from decaying leaf litter to determine if experimental atmospheric N deposition has lowered the diversity and altered the composition of the whole communities of bacteria and fungi (i.e., DNA-based) and well as its active members (i.e., RNA-based). In our experiment, experimental N deposition did not affect the composition, diversity, or richness of the total forest floor fungal community, but did lower the diversity (−8%), as well as altered the composition of the active fungal community. In contrast, neither the total nor active forest floor bacterial community was significantly affected by experimental N deposition. Our results suggest that future rates of atmospheric N deposition can fundamentally alter the organization of the saprotrophic soil fungal community, key mediators of C cycling in terrestrial environments.     

Land Use and Precipitation Affect Organic and Microbial Carbon Stocks and the Specific Metabolic Quotient in Soils of Eleven Ecosystems of Mt. Kilimanjaro,Tanzania

Tropical ecosystems are under increasing pressure of land‐use changes, strongly affecting the carbon cycle. Conversion from natural to agri‐cultural ecosystems is often accompanied by a decrease in the stocks of organic and microbial carbon (C_org, C_mic) as well as changes in microbial activity and litter decomposition. Eleven ecosystems along an elevation gradient on the slopes of Mt. Kilimanjaro were used to investigate impacts of land‐use changes on C_org and C_mic stocks as well as the specific metabolic respiration quotient (q_sCO₂) in surface soils. Six natural, two semi‐natural and three intensively used agricultural ecosystems were investigated on an elevation gradient from 950 to 3,880 m asl. To estimate the effects of precipitation, rainfall regimes of 3·6 and 20·0 mm were simulated. C_org stocks were controlled by water availability, temperature and net primary production. Agricultural management resulted in decreases of C_org and C_mic stocks by 38% and 76%, respectively. In addition, agricultural systems were characterized by low C_mic:C_org ratios, indicating a decline in available substrate. Enhanced land‐use intensity leads to increased q_sCO₂ (agricultural > semi‐natural > natural). The traditional homegardens stood out as a sustainable land‐use form with high substrate availability and microbial efficiency. Soil CO₂ efflux and q_sCO2 generally increased with precipitation level. We conclude that soils of Mt. Kilimanjaro's ecosystems are highly sensitive to land‐use changes and are vulnerable to changes in precipitation, especially at low elevations. Even though q_sCO₂ was measured under different water contents, it can be used as an indicator of ecosystem disturbances caused by land‐use and management practices. Copyright © 2015 John Wiley & Sons, Ltd.     

外源寡糖对奶山羊粪便微生物区系的影响

本试验旨在研究不同外源寡糖对奶山羊粪便微生物区系的影响.试验采用不完全拉丁方设计,选用平均体重为(32.80±2.45)kg、安装有永久性瘤胃瘘管的崂山奶山羊6只,分为6组,试验组羊分别饲喂在基础饲粮中添加1％的甘露寡糖(MOS组)、半乳甘露寡糖(GMOS组)、寡木糖(XOS组)、低聚异麦芽糖(IMO组)和果寡糖(FOS组)的试验饲粮,对照组(CT组)羊饲喂基础饲粮.共进行4期试验,每期35 d,其中预试期14d,正试期21 d.于正试期第1、7、14、21天晨饲前采集新鲜粪便,测定粪便中乳酸杆菌、双歧杆菌、大肠杆菌和沙门氏菌的数量.结果表明:与CT组相比,试验组乳酸杆菌数量均有所增加,其中FOS组第7天开始达到极显著水平(P＜0.01);试验组双歧杆菌数量增加,其中FOS组各采样时间均达到极显著水平(P＜0.01);试验组大肠杆菌数量有所降低,其中MOS组和FOS组第7天达到极显著水平(P＜0.01).本试验条件下,不同外源寡糖对增加奶山羊粪便乳酸杆菌、双歧杆菌数量,降低大肠杆菌数量的作用效果不同,其中果寡糖效果较明显.     

土壤微生物对不同退耕还林模式的响应

洪雅县位于四川盆地西南边缘，境内多低山丘陵。由于人们长期过度垦殖，致使林草植被遭到严重破坏，生态环境恶化。现已被四川省列为退耕还林的重点示范区，受到当地政府的高度重视和社会各界的广泛关注。近年来，人们在退耕还林模式的立地条件、树种配置、水土保持等方面进行了广泛研究。但缺乏从微生物角度探索退耕还林模式的研究。     

Balanced Fertilization along with Farmyard Manures Enhances Abundance of Microbial Groups and Their Resistance and Resilience against Heat Stress in a Semi-arid Inceptisol

The impact of long-term (36-year) application of balanced fertilizers and farmyard manures (FYM) on the abundance of microbial groups (bacteria, fungi, actinomycetes, Pseudomonas, Azotobacter, ammonia-oxidizing bacteria) and their resistance and resilience against heat stress was investigated in a semi-arid Inceptisol at New Delhi, India. Surface soils from selected treatments [control, nitrogen (N), N and phosphorus (P), NP and potassium (K), NPK + FYM] under a maize crop were assessed immediately after sampling (0-day) and at 1, 14, 28, and 56 day(s) after heat stress (48 °C for 24 h). The heat stress significantly reduced the microbial groups by 20 to 80%. Recovery after stress was 60 to 100% within 56 days. Resistance and resilience of fungi and actinomycetes were greater than other groups of organisms. Ammonia-oxidizing bacteria (AOB) were found to be most sensitive with the lowest resistance index. Application of NPK + FYM was most effective in enhancing the resistance and resilience of soil microorganisms against heat stress.     

棉蚜体表微生物对弗氏虫霉侵染的影响

对棉蚜体表微生物[芽枝霉(Cladosporium sp.),细菌—8(Bacillus—8)]和弗氏虫霉之间关系的研究结果表明:棉蚜体表微生物对弗氏虫霉[Entomophthora fresenii (Nowak) Gustafs,简称Ef]的孢子萌发、孢子形态变化、侵染力有很大影响。用体表微生物培养液浸Ef孢子能显著提高其萌发率。在Ef菌培养过程中加入体表微生物能产生相似于天然大孢子。将体表微生物和Ef菌剂混合用于田间防蚜,增效作用达29.2％～53.6％。所以笔者认为Ef和棉蚜体表微生物之间有密切的协生关系。     

吐温60和吐温80对反刍动物瘤胃和生产性能的影响

非离子表面活性剂(NIS)已经作为添加剂能有效地刺激需氧微生物的生长。本文综述了非离子型表面活性剂吐温60和吐温80在反刍动物营养中的应用。