A comparative study on the rumen microbial populations,hydrolytic enzyme activities and dry matter degradability between different species of ruminant

A comparative study among Korean native cow (Hanwoo), Holstein dairy cow, Korean native goat and crossbred sheep on the population and marker concentration of ruminal microbes, the activities of carboxymethylcellulase (CMCase), xylanase and amylase, and in situ dry matter (DM) degradability were conducted. Twelve ruminally cannulated animals, three of each species, were used. Animals were fed the same diet containing 40% formula feed and 60% rice straw at the level of 2.5% of body weight. Total viable microbial populations in the rumen fluid were significantly (P < 0.01) greater for bacteria and fungi in goat than those of Holstein. The protozoan population among ruminant species was the reverse from that of bacteria. The concentrations of 2,6‐diaminopimelic acid and chitin as markers for bacteria and fungi in the rumen fluid, respectively, were highest in goat, which is in accordance with the above population data. The concentration of aminoethylphosphonic acid as marker of protozoa was highest in Hanwoo and lowest in sheep (P < 0.01). Goat had the highest (P < 0.01) activities of all the enzymes investigated among ruminants. In situ effective degradation of the DM of rice straw was approximately 19% higher in the rumen of goat compared with other animals.     

Factors involved in the early pathogenesis of bovine Staphylococcus aureus mastitis with emphasis on bacterial adhesion and invasion. A review

Staphylococcus aureus is the most important and prevalent contagious mammary pathogen; it causes clinical and subclinical intramammary infection with serious economic loss and herd management problems in dairy cows. In vitro studies have shown that Staphylococcus aureus adheres to mammary epithelial cells and extracellular matrix components and invades into mammary epithelial as well as other mammary cells. Staphylococcus aureus strains from intramammary infection produce several cell surface-associated and extracellular secretory products. The exact pathogenic roles of most of the products and their effects on adhesion and invasion are not well evaluated. It is also known that mammary epithelial cell-associated molecules and extracellular matrix components interact with S. aureus during the pathogenesis of mastitis, but their roles on adhesion and invasion have not been characterized. The adhesion of S. aureus to epithelial cells may involve non-specific physicochemical interactions and/or specific interactions between bacterial cell-associated ligands and host cell surface receptors. In vitro adhesion depends on the S. aureus strain, the growth phase of the bacteria, the growth medium and the origin of the epithelial cells. Adhesion is hypothesized to be a prerequisite and crucial early step for mammary gland infection. Staphylococcus aureus invades mammary epithelial cells. It also invades other cells such as endothelial cells and fibroblasts. Bacteria are found enclosed in membrane bound vacuoles in the cytoplasm of mammary epithelial cells. Recent observations indicate that S. aureus escapes from the phagosome into the cytoplasm and induces apoptosis. The invasion into mammary epithelial cells may occur through an endocytic process that requires involvement of elements of the cytoskeleton or by direct binding of bacteria to epithelial cells through a process mediated by specific receptors that needs de novo protein synthesis by both cells. Thus, the recurrent subclinical infection may result from this intracellular existence of bacteria that are protected from host defenses and effects of antibiotics. This review emphasizes on recent findings on S. aureus adhesion to mammary epithelial cells and extracellular matrix components and invasion into mammary epithelial cells.     

Presence of ISS1-like insertion sequence in wild type Streptococcus uberis strains isolated from cases of bovine mastitis

Streptococcus uberis is a major cause of environmental mastitis worldwide. In spite of significant economic losses caused by S. uberis in many well-managed dairy herds, virulence factors and mechanisms associated with the pathogenesis of S. uberis mastitis are not well known. The ability of S. uberis to attach to and internalize into mammary epithelial cells and subsequent intracellular survival enables it to avoid host defense mechanisms. Research to determine virulence factors responsible for these pathogenic strategies involved creating a random chromosomal mutant library of S. uberis strain UT888 using the thermosensitive plasmid pGh9:ISS1 mutagenesis system. During Southern blot analysis of the mutant library, an endogenous element similar to ISS1 insertion sequence of Lactococcus lactis was found. ISS1 is a transposable bacterial insertion sequence isolated originally from L. lactis and are small phenotypically cryptic sequences of DNA with a simple genetic organization and capable of inserting at multiple sites in a target molecule. They are flanked by inverted repeats; generally encode their own transposition functions. A total of 29 of 34 wild type strains of S. uberis evaluated were positive for ISS1 by Southern blot. Insertion of ISS1 might have a significant phenotypic and genotypic role in the S. uberis genome because of its ability to transpose within the genome.     

聚合果属生物炭引起的咸水灌溉下土壤养分有效性和番茄生长变化

Thermally modified organic materials commonly known as biochar have gained popularity of being used as a soil amendment.Little information, however, is available on the role of biochar in alleviating the negative impacts of saline water on soil productivity and plant growth. This study, therefore, was conducted to investigate the effects of Conocarpus biochar(BC) and organic farm residues(FR) at different application rates of 0.0%(control), 4.0% and 8.0%(weight/weight) on yield and quality of tomatoes grown on a sandy soil under drip irrigation with saline or non-saline water. The availability of P, K, Fe, Mn, Zn and Cu to plants was also investigated. The results demonstrated clearly that addition of BC or FR increased the vegetative growth, yield and quality parameters in all irrigation treatments. It was found that salt stress adversely affected soil productivity, as indicated by the lower vegetative growth and yield components of tomato plants. However, this suppressing effect on the vegetative growth and yield tended to decline with application of FR or BC, especially at the high application rate and in the presence of biochar. Under saline irrigation system, for instance, the total tomato yield increased over the control by 14.0%–43.3% with BC and by 3.9%–35.6% with FR. These could be attributed to enhancement effects of FR or BC on soil properties, as indicated by increases in soil organic matter content and nutrient availability. Therefore, biochar may be effectively used as a soil amendment for enhancing the productivity of salt-affected sandy soils under arid conditions.     

Alberta油砂地区在两种水文流域森林土壤酸化敏感性研究

Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta. We evaluated the sensitivity of forest soils to acidification in two watersheds （Lake 287 and Lake 185） with contrasting hydrological regimes as a part of a larger project assessing the role of N and S cycling in soil acidification in forest ecosystems. Fifty six forest soil samples were collected from the two watersheds by horizon from 10 monitoring plots dominated by either jack pine （Pinus banksiana） or aspen （Populus tremuloides）. Soils in the two watersheds were extremely to moderately acidic with pH （CaCl2） ranging from 2.83 to 4.91. Soil acid-base chemistry variables such as pH, base saturation, Al saturation, and acid-buffering capacity measured using the acetic acid equilibrium procedure indicated that soils in Lake 287 were more acidified than those in Lake 185. Acid-buffering capacity decreased in the order of forest floor 〉 subsurface mineral soil 〉 surface mineral soil. The most dramatic differences in percent Ca and Al saturations between the two watersheds were found in the surface mineral soil horizon. Percent Ca and Al saturation in the surface mineral soil in Lake 287 were 15% and 70%, respectively; the percent Ca saturation value fell within a critical range proposed in the literature that indicates soil acidification. Our results suggest that the soils in the two watersheds have low acid buffering capacity and would be sensitive to increased acidic deposition in the region.     

pGh9:ISS1 transpositional mutations in Streptococcus uberis UT888 causes reduced bacterial adherence to and internalization into bovine mammary epithelial cells

Streptococcus uberis is an important mastitis pathogen that affects dairy cows worldwide. In spite of the economic impact caused by the high prevalence of S. uberis intramammary infections (IMI) in many well-managed dairy herds, pathogenic strategies and associated virulence factors of S. uberis are not well understood. It has been shown that S. uberis attaches to and internalizes into mammary epithelial cells and can survive inside cells for extended periods of time. We hypothesize that early attachment to and internalization into mammary epithelial cells is a critical step for the establishment of intramammary infection. The aim of this study is to identify and characterize chromosomally encoded virulence factors of S. uberis that allow early bacterial attachment to and internalization into mammary epithelial cells. A common approach used to identify virulence factors is by generating random insertion mutants that are defective in adherence to and internalization into mammary epithelial cells using pGh9:ISS1 mutagenesis system. A random insertion mutant library of S. uberis strain UT888 was created using a thermo-sensitive plasmid pGh9:ISS1 carrying ISS1 insertion sequence. Integration of the insertion sequence into the chromosome of these mutant clones was confirmed by PCR and Southern blot. Southern blot analysis of mutant clones also showed that insertional integration was random. Of 1000 random chromosomal insertion mutants of S. uberis strain UT888 screened, 32 had significantly reduced ability to adhere to and internalize into mammary epithelial cells. Chromosomal mapping of insertion sequence integration sites in some of these defective mutants showed integration into penicillin binding protein 2A (pbp2A), sensor histidine kinase, tetR family regulatory protein, phosphoribosylaminoimidazole carboxylase catalytic subunit (purE), lactose phosphotransferase, phosphoribosylamine glycine ligase (purD), and other genes involved in metabolic activities. These proteins may have a significant role in early bacterial colonization of the mammary gland during infection.     

Bovine Mastitis in Selected Areas of Southern Ethiopia

A study on bovine mastitis, designed to determine the causal agents, prevalence of infection and impact of risk factors in three cattle breeds, was conducted in selected areas of southern Ethiopia. A total of 307 lactating and non-lactating cows, of which 162 were indigenous Zebu, 85 Jersey and 60 Holstein-Friesian, were examined by clinical examination and the California mastitis (CMT) test. Of these, 40.4% were positive by CMT and bacteriology for clinical or subclinical mastitis, with prevalence rates of 37.1% and 62.9%, respectively. Out of 1133 quarters examined, 212 (18.7%) were found to be infected, 83 (39.2%) clinically and 129 (60.8%) subclinically. The prevalence of mastitis was significantly higher in Holstein-Friesian than in indigenous Zebu, in non-lactating cows than in lactating cows, in the early lactation stage than in the mid-lactation stage, in cows with lesions and/or tick infestation on skin of udder and/or teats than in cows without this factor, and in the wet season than in the dry season. Mastitis increased with parity number (R = 0.9). Of 248 CMT and clinically positive udder quarter samples analysed microbiologically, 212 were culturally positive for known mastitis pathogens and 36 were negative. Of the 199 positive samples, Staphylococcus accounted for 39.2%, Streptococcus for 23.6%, coliforms for 14.1%, Micrococcus and Bacillus species for 8.0% each and Actinomyces or Arcanobacterium (Corynebacterium) for 7.0%. It was concluded that there was a high prevalence of clinical and subclinical mastitis, mainly caused by Staphylococcus aureus, Streptococcus agalactiae and Escherichia coli, in this study area.     

Host-pathogen gene expression profiles during infection of primary bovine mammary epithelial cells with Escherichia coli strains associated with acute or persistent bovine mastitis

Escherichia coli intramammary infection (IMI) is often acute with local and systemic clinical manifestations that clear within 7 days. However, if not diagnosed early and treated, E. coli IMI could result in generalized systemic reaction and death. Persistent E. coli IMI is characterized by mild clinical manifestations followed by acute episodes of clinical mastitis during lactation. Factors responsible for pathogenesis of E. coli IMI and variation in clinical manifestations are not known. There are studies indicating that the outcome of E. coli IMI is mainly determined by cow factors. However, recent research demonstrated that virulence attributes of E. coli strains have significant impact on the outcome of E. coli IMI. The aims of this study were; (a) to compare gene expression profiles of PBMEC cocultured with strains of E. coli associated with acute or persistent IMI and; (b) to identify genes of E. coli induced during bacterial interaction with PBMEC. Utilizing cDNA we analyzed gene expression patterns of PBMEC cocultured with strains of E. coli using non-treated PBMEC as negative control. We evaluated also expression patterns of virulence associated genes of E. coli after co-culture with PBMEC using qRT-PCR. Our results showed that infection by both strains induced increased expression of pro-inflammatory cytokines, chemokines and innate immune response and apoptosis related genes. Our qRT-PCR results showed significant up-regulation of ler, eae, flic and iutA genes mainly in the strains of E. coli associated with persistent IMI. The pathogenesis and clinical severity of E. coli IMI may be determined by combined effects of host-pathogen factors.     

土壤污染修复中的生物炭-微生物交互作用研究进展

近年来，生物炭在污染土壤修复中的研究与应用受到广泛关注，且已被证实对于修复土壤重金属及有机污染具有显著的效果。生物炭可以改善土壤性质，影响土壤微生物群落，实现生物炭介导的微生物土壤污染修复。本文综述了生物炭对微生物的积极作用，包括提供额外生存环境、提供营养物质和改善原有栖息地[土壤团聚性、pH、阳离子交换能力（CEC）和酶活性]。这些影响将导致微生物丰度、活性和群落结构的变化。然而，生物炭所携带的可能威胁微生物群落的有毒物质也不应被忽视，如多环芳烃、呋喃等；同时生物炭在高温热解过程中产生的持久性自由基也会对微生物产生毒性。本文还讨论了生物炭介导的微生物修复技术在去除土壤污染物方面的应用现状，最后对生物炭-微生物交互作用在土壤污染修复中的研究方向提出了展望。