Detritivorous earthworms modify microbial community structure and accelerate plant residue decomposition

The impact of detritivorous earthworms (Eisenia andrei) on microbial community structure and function in grape marc, a lignocellulosic enriched plant residue, was investigated in a mesocosm experiment. Analysis of carbon and nitrogen pools was also carried out in order to evaluate how changes in microbial communities affect plant residue decomposition. The grape marc was completely processed after fifteen days as a result of the high density of earthworms present and the rapid gut transit time. Eisenia andrei had a large impact on the structure of the microbial community, as revealed by phospholipid fatty acid analysis. Earthworm activity reduced the abundance of both bacterial (except for Gram-negative bacteria) and fungal PLFA biomarkers relative to the control values. Decreases in microbial activity and in protease and cellulase activities were also attributable to the presence of earthworms. Moreover, earthworms strongly modified the substrate utilization patterns of microbial communities, as revealed by BIOLOG analysis. The presence of earthworms led to an increase in the utilization of some amino acids and polymers, which reached a higher substrate diversity value than that in the control mesocosm. The differences in microbial communities were accompanied by a reduction in the total C content and the labile C pool, relative to the control, although there were no significant differences in either cellulose or hemicellulose contents. However, total N content increased in both mesocosms – with and without earthworms – and the concentration of NH₄⁺ was also enhanced by earthworm activity. The results indicate that detritivorous earthworms play a key role in decomposing fresh plant residues in the short term via their intensive interactions with microbial communities.     

Chemical composition of the Lippia origanoides essential oils and their antigenotoxicity against bleomycin-induced DNA damage

The present work evaluated the chemical composition of the essential oils (EO) obtained from Lippia origanoides and their DNA protective effect against bleomycin-induced genotoxicity. L. origanoides EO chemical composition was determined by gas chromatography–mass spectrometry (GC–MS). The major compounds of the L. origanoides EOs were thymol (34–58%) and carvacrol (26%). The antigenotoxic effects of the EOs, major compounds and standard compound (epigallocatechin gallate) were assayed in co-incubation procedures using the SOS chromotest in Escherichia coli. Both EOs and their major compounds protected bacterial cells against bleomycin-induced genotoxicity indicating that these two compounds were principally responsible for the antigenotoxicity detected in the oils. Thymol and carvacrol antigenotoxicity was lower than those observed with epigallocatechin gallate. The results were discussed in relation to the chemopreventive potential of L. origanoides EOs and their major components, carvacrol and thymol.     

Bioprospection of Microalgae and Cyanobacteria as Biocontrol Agents Against Vibrio campbellii and Their Use in White Shrimp Litopenaeus vannamei Culture

Vibrio spp. are the most common and harmful shrimp pathogenic bacteria; however, microalgae and cyanobacteria have the ability to produce antimicrobial substances against these species. In this study, the organic and aqueous extracts of 28 species of marine microalgae and cyanobacteria were screened against Vibrio campbellii M1. Two of these phytoplankton species with antibacterial activity in aqueous extracts (Dunaliella tertiolecta and Skeletonema costatum) and nontoxic to brine shrimp Artemia franciscana nauplii were used to evaluate their anti‐Vibrio effect when used as green‐water cultures in Vibrio‐challenged white shrimp Litopenaeus vannamei cultures. No differences in mortality of juvenile L. vannamei were observed between treatments tested, suggesting that the pathogenicity of V. campbellii could be related to the growth stage of shrimp. The proximal composition of D. tertiolecta and S. costatum was in the recommended range for penaeid shrimp nutrition, allowing shrimp supplemented with these microalgae to have significantly greater total length and weight than control shrimp. Shrimp supplemented with S. costatum presented the highest values of organic mass (11.48 mg/organism) and growth rate (0.31 mg/d) in comparison to D. tertiolecta. These results indicate that microalgae are not only capable of producing antibacterial compounds against Vibrio but can also help shrimp nutrition.     

Progeny Production of the Copepods Pseudodiaptomus euryhalinus and Tisbe monozota in Monospecific and Mixed Cultures

The objective of this research was to culture the calanoid copepod Pseudodiaptomus euryhalinus, Johnson 1939, and the harpacticoid Tisbe monozota, Bowman, 1962, in monospecific and combined cultures (P. euryhalinus : T. monozota at 1:1, 2:1, and 1:2 starting ratios), and to compare the nauplii, copepodite, and adult production. Mean total production ranged from 740.3 ± 137.5 organisms/L (P. euryhalinus) to 884.3 ± 489.7 organisms/L (T. monozota) for monospecific cultures. The 1:1 ratio mixed cultures gave 780.4 ± 155.8 organisms/L, those with the 2:1 and 1:2 P. euryhalinus and T. monozota starting ratios produced 710.1 ± 195.2 and 799.7 ± 232.5 organisms/L, respectively, and there were no significant difference among treatments. All mixed cultures gave significantly lower copepodite productions than the monocultures of each species. In addition, the tendency to a decreased progeny production of the initial females of T. monozota indicates that the outcome of long‐term mixed cultures would production either a high dominance of P. euryhalinus, or monocultures of this species .     

对FC株猪源性肠毒素型大肠杆菌致病因子的研究

FC菌株是一株从腹泻仔猪粪便中分离的肠毒素型大肠杆菌(Enterotoxigenic E.coli,ETEC)。在MRHA反应中,本菌能凝集人O型、豚鼠、马、绵羊、牛、鸡和兔的红细胞,对人O型和豚鼠红细胞有很高的血凝性,血抗K88和K99血清不能抑制其对豚鼠和绵羊红细胞的血凝。在体外小肠上皮细胞吸附试验中,本菌对仔猪小肠上皮细胞具有强烈的吸附作用;透射电镜和扫描电镜观察证实了FC株菌除表面具有一种纤毛样结构外,还能定居在仔猪小肠段。血清学试验结果表明,本菌的O抗原属于O101。K88和987P两种抗血清均不能凝集本菌,而K99和F41抗血清均可凝集。对纯化的FC株菌粘着素抗原作等电聚焦和聚丙烯酰胺凝胶电泳分析,结果表明,该菌的粘着素是由等电点分别为4.61和9.78,分子量分别为29500和17500的两种蛋白质抗原所组成。此外,用乳鼠胃内投服试验和兔肠结扎试验证明,该菌只产生热稳定肠毒素。总之,本菌是一株能产生ST的K99,F41的肠毒素型大肠杆菌。     

Development of a functional scoring system in dogs with acute spinal cord injuries

OBJECTIVES: To develop and compare the reliability of 2 methods of scoring pelvic limb gait in dogs recovering from thoracolumbar spinal cord injuries and to use this scoring system to determine the rate and level of functional recovery of dogs with acute thoracolumbar intervertebral disk herniations. ANIMALS: 46 dogs with spinal cord injuries resulting from intervertebral disk herniations. PROCEDURE: Dogs' gaits were videotaped at different time intervals after injury. In phase 1 of the study, the stages of recovery of pelvic limb function were identified, and a numeric scoring system was devised to reflect that recovery. In phase 2, pelvic limb gait was scored by different observers, using a numeric and a visual analog scale. Intra- and interobserver coefficients of variability of both methods were compared. In phase 3, pelvic limb function was scored, using the numeric scale at various intervals after acute thoracolumbar disk herniations. RESULTS: The numeric scale was significantly more reliable than the visual analog scale when both intra- and interobserver coefficients of variability were evaluated. Dogs that were paraplegic with no deep pain sensation recovered at different rates during the first 3 months, whereas dogs that were paraplegic with deep pain sensation typically recovered within 1 month of injury. CONCLUSIONS: Pelvic limb gait of dogs recovering from thoracolumbar spinal cord injuries can be reliably quantified, using a numeric scale. This scale will facilitate the performance of clinical trials aimed at improving the outcome of acute spinal cord injuries.     

Crude protein fractions in common vetch (Vicia sativa L.) fresh forage during pod filling

Crude protein (CP) of forages can be separated into fractions of differentiated abilities to provide available amino acids in the lower gut of ruminants. This knowledge is critical to develop feeding systems and to predict animal responses. We have measured during two growing seasons (1996 to 1997 and 1997 to 1998) the CP fractions of common vetch fresh forage with the objective being to assess the influence of maturity on concentration of CP fractions (as a percentage of total CP) and fraction yields. Fraction B2, which represents true protein of intermediate ruminal degradation rate, was the largest single fraction in common vetch forage (about 40% of CP across seasons and maturity stages). Soluble fractions (A plus B1) were less than 50% of total CP while the unavailable fraction C ranged from 4 to 8% of total CP. As a result, the remaining fraction B3 (true protein of very low degradation rate) only represented 2 to 9% of total CP. Concentration and yield of fraction B3 increased (P < 0.05) from flowering to pod-filling. Results showed that undegraded dietary protein represented a small proportion of total CP in common vetch forage. Moving the harvesting stage from flowering to the pod filling phase allowed for greater yield of undegraded dietary protein.     

Effect of different methods of administration of ivermectin on its efficacy against the shedding of gastrointestinal nematode eggs by gazelles

Seven different methods of administering ivermectin to gazelles were compared: subcutaneous injection, direct oral administration, administration in individual feeds, administration in a herd feed, direct oral administration of a second ivermectin formulation, administration in individual water supplies, and administration in the herd's water supply. The first five treatments were effective, as monitored by faecal egg count reduction tests, and administration in individual feeds or in a herd feed avoided the need to capture the animals, with the attendant risk of mortality. Of the factors associated with the recipients (species, sex, age and inbreeding coefficient) age was the only significant factor for the efficacy of the treatment. Oral or subcutaneous, individual or collective, and direct or indirect administrations were equally satisfactory for the treatment of all the parasite groups studied. Only when parasitic problems were due to Nematodirus species did direct administration to individual animals appear to be preferable.     

Fusobacteriosis in captive wild-caught pronghorns (Antilocapra americana)

An outbreak of Fusobacterium necrophorum-induced septicemia occurred in a group of 40 captive wild-caught pronghorns (Antilocapra americana). Primary pododermatitis or necrotic stomatitis progressed to produce fatal septicemia with metastatic lesions in the forestomachs, lung, liver, and cecum in 38 of the animals. Two remaining animals were euthanatized because of chronic pododermatitis. Housing the animals in a pasture previously used by bovids and heavy rains with persistence of ground water pools in the pasture were contributing factors in the pathogenesis of this outbreak.