A gene targeting suicide vector for Streptococcus bovis

A gene-targeting suicide vector for Streptococcus bovis has been constructed using the Escherichia coli/Streptococcus shuttle plasmid, pMU1328, and a region derived from the broad host-range, Gram-positive transposon, Tn916. This suicide plasmid replicates autonomously in E. coli, but not in Strep. bovis or Strep. bovis Tn916. Under positive selection, the plasmid was shown to integrate into Strep. bovis Tn916 chromosomal DNA at a frequency of 3 x 10(-8) cell-1 and was stably maintained for at least 100 generations in the absence of selection. This is the first report of a recombination system in ruminal bacteria. The ability to target genes, knock out specific functions or introduce novel genes into these micro-organisms will allow ruminal species to be manipulated and may eventually lead to improved animal production

Eficiência microbiana, fluxo de compostos nitrogenados no abomaso, amônia e pH ruminais, em bovinos recebendo dietas contendo feno de capim-tifton 85 de diferentes idades de rebrota Microbial efficiency, abomasal nitrogen compounds flow, ruminal ammonia and ruminal pH in cattle fed diets containing tifton 85 bermudagrass hays at different regrowth ages

Avaliaram-se a eficiência de síntese microbiana, o fluxo de compostos nitrogenados no abomaso, o balanço de compostos nitrogenados, a taxa de passagem da digesta ruminal, a concentração de amônia e o pH ruminais, em bovinos recebendo rações contendo feno de capim-tifton 85 de diferentes idades de rebrota. Utilizaram-se quatro animais zebu, com peso médio de 340 kg, fistulados no rúmen e abomaso, distribuídos em um delineamento em quadrado latino 4 x 4. Todas as rações continham 60% de volumoso e 40% de concentrado. O volumoso foi constituído de feno de capim-tifton 85 de 28, 35, 42 e 56 dias de idade e o concentrado continha fubá de milho e mistura mineral. Os microorganismos ruminais foram quantificados utilizando-se as bases purinas como indicador. O pH e N-amoniacal foram mensurados, no fluido ruminal, antes e 2; 4 e 6 horas após o fornecimento da ração. A taxa de passagem foi determinada pelo modelo unicompartimental, utilizando-se o óxido crômico como indicador. As eficiências de síntese microbiana não foram influenciadas pela idade do feno na ração, apresentando valores médios de 31,32 g Nbact/kg MODR; 30,74 g Nbact/kg CHODR; 337,4 g MSbact/kg CHODR; e 12,5 g PBbact/100 g NDT. Estimaram-se máximos fluxos de compostos nitrogenados totais, amoniacais e não-amoniacais, de 119,0; 9,76; e 109,6 g/dia, com a inclusão de feno com 39,7; 37,6; e 39,9 dias de idade, respectivamente, e fluxo de compostos nitrogenados bacterianos de 80,54 g/dia, em média. O balanço de nitrogênio, a taxa de passagem, as concentrações de amônia e o pH ruminais também não foram influenciados pela idade do feno na ração, encontrando-se valores de 30,67 g/dia; 3,2%/h; 9,7 mg/100mL (máximo às 1,38h) e 6,08 (mínimo às 6,64h), respectivamente.<br>The microbial efficiency synthesis, the abomasum nitrogen compounds flow, the nitrogen compounds balance, the passage rate of ruminal digest, the ruminal ammonia concentration and ruminal pH in cattle fed diets containing Tifton 85 bermudagrass hay with different regrowth ages were evaluated. Four rumen and abomasum fistulated zebu cattle with average 340 kg LW were allotted in a 4x4 Latin square. All diets contained 60:40 forage to concentrate ratio. The forage was consisted in Tifton 85 bermudagrass hay with 28, 35, 42 and 56 days of age, and the concentrate contained corn meal and mineral mix. The amount of microorganisms was determined using purines as a marker. The pH and N-ammonia were determined in the ruminal fluid before and 2, 4 and 6 hours after feeding. The passage rate was determined by unicompartimental model using the chromic oxide as a marker. The microbial efficiency synthesis was not affected by the age of the hay in the diet, presenting mean values of 31.32 g Nbact/kg RDOM, 30.74 g Nbact/kg RDCHO, 33.74 g DMbact/kg RDCHO and 12.5 g CPbact/100 g TDN. The maximum estimates of total nitrogen compound flows, ammonia and non ammonia were 119.0, 9.76 and 109.6 g/day, with the inclusion of hay with 39.7; 37.6 and 39.9 days of regrowth age, respectively and the bacterial nitrogen compounds flow of 80.54 an average. Nitrogen balance, passage rate, ruminal ammonia concentration and ruminal pH also were not affected by the age of the hay, with values of 30.67 g/day, 3.2%/h, 9.7 mg/100mL (maximum at 1.38h) and 6.08 (minimum at 6.64 h), respectively