Influence of the Indoleacetic Acid-Lysine Synthetase Gene (iaaL) of Pseudomonas syringae subsp. savastanoi on Yield Attributes of Potatoes

The iaaL gene of Pseudomonas syringae subsp. savastanoi encodes an indoleacetic acid-lysine synthetase which conjugates free indoleacetic acid (IAA) with lysine. lAA-lys is biologically less active than free IAA. The iaaL coding region was expressed under the control of the cauliflower mosaic virus 35S promoter and transgenic potato plants were produced (Spena et al. 1991). 35S iaaL potato plants are characterized by increased internodal length and epinastic bending of older leaves. In three greenhouse experiments with plants grown in pots of different size and in two growth chamber experiments tuber number increased in iaaL transgenic plants compared to untransformed and vector-transformed controls of the same genotype. The increase in tuber numbers observed under controlled conditions was reflected in tuber yield which increased in the pot grown transgenics.     

Biofilm bacteria: formation and comparative susceptibility to antibiotics

The Calgary Biofilm Device (CBD) was used to form bacterial biofilms of selected veterinary gram-negative and gram-positive pathogenic bacteria from cattle, sheep, pigs, chicken, and turkeys. The minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) of ampicillin, ceftiofur, cloxacillin, oxytetracycline, penicillin G, streptomycin, tetracycline, enrofloxacin, erythromycin, gentamicin, tilmicosin, and trimethoprim-sulfadoxine for gram-positive and -negative bacteria were determined. Bacterial biofilms were readily formed on the CBD under selected conditions. The biofilms consisted of microcolonies encased in extracellular polysaccharide material. Biofilms composed of Arcanobacterium (Actinomyces) pyogenes, Staphylococcus aureus, Staphylococcus hyicus, Streptococcus agalactiae, Corynebacterium renale, or Corynebacterium pseudotuberculosis were not killed by the antibiotics tested but as planktonic bacteria they were sensitive at low concentrations. Biofilm and planktonic Streptococcus dysgalactiae and Streptococcus suis were sensitive to penicillin, ceftiofur, cloxacillin, ampicillin, and oxytetracycline. Planktonic Escherichia coli were sensitive to enrofloxacin, gentamicin, oxytetracycline and trimethoprim/ sulfadoxine. Enrofloxacin and gentamicin were the most effective antibiotics against E. coli growing as a biofilm. Salmonella spp. and Pseudomonas aeruginosa isolates growing as planktonic populations were sensitive to enrofloxacin, gentamicin, ampicillin, oxytetracycline, and trimethoprim/sulfadoxine, but as a biofilm, these bacteria were only sensitive to enrofloxacin. Planktonic and biofilm Pasteurella multocida and Mannheimia haemolytica had similar antibiotic sensitivity profiles and were sensitive to most of the antibiotics tested. The CBD provides a valuable new technology that can be used to select antibiotics that are able to kill bacteria growing as biofilms.     

Anthelmhntic effects of injectable and oral paste formulations of ivermectin against 28-day infections of parascaris equorum

Efficacy of ivermectin treatment (0.2 mg/kg) against 28-day experimental infections of Parascaris equorum was determined in 18 pony foals6–17.5 weeks old. There were 6 foals in each group: nontreated control, ivermectin injectable or oral paste. In comparison with larvae found in the nontreated controls, ivermectin injectable or paste was 96.0% and 99.9% efficacious. There was a distinct difference in drug effect against the larger (ca 26mm.) vs the smaller (13–19mm) larvae by the 2 formulations of ivermectin. There were no adverse signs related to treatment of the young foals.     

Identification of a potentially important antigen of pasteurella haemolytica

To identify antigens which may be important for stimulating immunity to pneumonic pasteurellosis, a bovine antiserum to whole P. haemolytica was used to screen a recombinant lambda gt11/P. haemolytica expression library. One of the recombinant bacteriophage clones identified with the bovine antiserum, SW20C, expressed a fusion protein which was also recognized by rabbit antiserum to partially purified P. haemolytica culture supernatant and was found to be immunogenic in guinea pigs. The guinea pig antibody recognized a 100 kDa protein in P. haemolytica cell lysates. Sequence analysis of the cloned DNA from SW20C identified a fragment of 1443 bp with a small open reading frame that was contiguous with the lacZ sequence. The 153 bp P. haemolytica-specific open reading frame encoded a polypeptide of approximately 6kDa. Homology searches of Genbank and the EMBL data bases revealed no homology of this open reading frame with any other bacterial sequences including P. haemolytica leukotoxin and Ssa1. Evaluation of sera from calves that were scored either susceptible or resistant to experimental pneumonic pasteurellosis demonstrated a significant (P < 0.001) correlation between the intensity of the antibody response to the SW20C antigen and resistance to disease.     

Survey of internal parasites in Western Australian pig herds. 1. Prevalence

Between September 1982 and March 1984, 101 Western Australian piggeries with 15 or more sows were surveyed to determine the prevalence of internal parasites and examine the relationship between parasitism and management practices. Faecal samples were collected from 20 pigs in 4 age groups in randomly selected piggeries, and examined for the presence of eggs of helminth parasites and protozoan cysts. Evidence of nematode parasites was found in 79% of piggeries. Sows were more commonly affected than other classes of pigs with worm eggs being found in 68% of herds. Oesophagostomum spp was the most prevalent worm species, being found in pigs from 65% of piggeries and in sows in 60% of herds. Ascaris suum was the most common species of worm found in growing pigs. There was no evidence of infection with either Metastrongylus spp or Strongyloides spp in any of the herds sampled. Oocysts of coccidia were found in pigs from 56% of piggeries and Balantidium coli cysts were detected in pigs from 42% of piggeries sampled.     

Effect of season and lactation on postpartum fertility of Polypay, Dorset, St. Croix and Targhee ewes

The objective of this study was to compare rebreeding activities of spring- vs fall-lambing Polypay, Dorset, St. Croix and Targhee ewes that either suckled their lambs for 40 d or had lambs weaned at birth. Seasonal effects of male fertility were reduced by utilizing an excess number of fertile rams in the spring. Plasma concentrations of progesterone were monitored to assess days to the first normal ovulation, days to conception and estrous vs anestrous activity. Breed, season and lactation affected the rebreeding performance. Dorset ewes had similar conception rates between spring and fall but a shorter interval from lambing to first ovulation in the fall. Polypay and Targhee ewes were the opposite; they had higher conception rates in fall than in spring matings with no seasonal influence on postpartum interval. Postpartum ewes in the fall had higher conception rates, and fewer of these ewes became anestrous or had estrous cycles of abnormal duration than of those ewes lambing in the spring. Ewes that suckled for 40 d in the spring had delayed estrous activity, but when these ewes became estrual they had higher conception rates than ewes whose lambs were weaned at birth. Lactation had no inhibitory affect on the postpartum interval of fall lambing ewes. These data suggest that the response of different breeds to various components of postpartum fertility varies with season and management of the flock.     

Hemagglutination and hemagglutination inhibition of turkey red blood cells with Mycoplasma hyopneumoniae

The ability of Mycoplasma hyopneumoniae to agglutinate RBC was evaluated to develop an in vitro cytadsorption assay. Using swine RBC in a microtitration hemagglutination test, no agglutination or partial agglutination was detected. Comparison of RBC from various other species indicated that improved hemagglutination was obtained with RBC from turkeys. This hemagglutination was detected only when mycoplasma cells used in the assay had been frozen and thawed, heated at 50 C for 30 minutes, or treated with trypsin. Treatment of RBC with trypsin or neuraminidase enhanced hemagglutination. Possible surface lectin activity in M hyopneumoniae was evaluated by use of carbohydrates in a blocking assay; hemagglutination was not inhibited by any of 13 carbohydrates evaluated. Mycoplasma hyopneumoniae convalescent porcine serum and monoclonal antibodies against 2 M hyopneumoniae immunogens of molecular weights of 64,000 and 41,000 inhibited hemagglutination.     

西瓜蔓枯病研究 Ⅰ.症状及病原

本文详细报道了西瓜蔓枯病的症状和病原菌的形态特点,并鉴定其有性阶段为Mycosphaerellamelonis(Pass)Chiu et Walker,无性阶段为Ascochyta-cucumis Fautr et Roum.此外,还在其他瓜类作物上作了病原菌的致病性试验.