In three replicate trials, a total of 36 pigs that had been cannulated at the terminal ileum were used to determine the effects of a Saccharomyces cerevisiae culture in a phase feeding program (phase I was d 0 to 7 and phase II was d 8 to 21) on performance, ileal microflora, and short-chain fatty acids in weanling pigs. Pigs were cannulated at approximately 12 d of age, weaned at 17 d of age, and randomly assigned to one of three treatments: 1) a pelleted phase feeding program, 2) a similar program with the inclusion of a live S. cerevisiae culture (1 g/ kg), and 3) a nonpelleted feeding program otherwise similar to program 2. Ileal samples were collected at 17, 20, 24, 27, 31, 34, and 38 d of age, and samples were analyzed for total E. coli, streptococci, lactobacilli, yeast, short-chain fatty acids, pH, and dry matter. Performance data were also collected. At 41 d of age, pigs were killed and digesta were collected from various regions of the gastrointestinal tract. Total intake was less for pigs fed the control diet than for pigs fed the yeast diets, and overall gains tended to be greater for pigs fed diets including yeast. Treatment differences were not observed for ileal microflora or short-chain fatty acids in samples obtained from cannulas or from the various sites of the gastrointestinal tract. Inclusion of a live yeast culture in weanling pig diets affected intake and performance but did not alter tested intestinal microflora or net concentrations of fermentation products.
Escherichia coli produces biofilms in response to the small molecule autoinducer-2 (AI-2), a product of the LuxS enzyme. LuxS is part of the activated methyl cycle and could also affect biofilm development by AI-2-independent effects on metabolism. A luxS deletion mutant of E. coli W3110 and an inducible plasmid-luxS-complemented strain were used to identify AI-2-independent phenotypes. Differential interference contrast microscopy revealed distinct surface colonization patterns. Confocal microscopy followed by quantitative image analysis determined differences in biofilm topography correlating with luxS expression; deletion mutant biofilms had a 'spreading' phenotype, whereas the complement had a 'climbing' phenotype. Addition of exogenous 4,5-dihydroxy-2,3-pentanedione (DPD), an AI-2 precursor, to the deletion mutant increased biofilm height and biomass, whereas addition of the methyl donor S-adenosyl methionine or aspartate prevented the luxS-complemented strain from producing a thick biofilm. The luxS-complemented strain autoaggregated, indicating that fimbriae production was inhibited, which was confirmed by transmission electron microscopy. DPD could not induce autoaggregation in the deletion mutant, demonstrating that fimbriation was an AI-2-independent phenotype. Carbon utilization was affected by LuxS, potentially contributing to the observed phenotypic differences. Overall, the work demonstrated that LuxS affected E. coli biofilm formation independently of AI-2 and could assist in adapting to diverse conditions.
An in vitro system to measure the adhesion of bacteria to human, eukaryotic cells was devised. Adhesion indices for test strains of bacteria could be calculated. Significant differences were then observed between various strains of Escherichia coli from a variety of sources, in their ability to adhere. The possible applications of the test, especially for the routine screening of bacteria for adhesion and for inhibitors of attachment, were considered.
In three experiments, weanling pigs were used to investigate the effect of feeding .5% galactosyl lactose in a simple corn-soy diet on nutrient digestibility, selected ileal microbial concentrations, fermentation acids, and performance. In Exp. 1, 20 21-d-old weaned pigs in two replicate trials were fed either a 19% CP corn and soybean meal diet or a similar diet containing .5% galactosyl lactose. Feces and urine were collected over a 3-wk period to determine apparent CP and energy digestibilities. Apparent digestibilities of CP and energy were not different between treatments. In Exp. 2, 24 14-d-old nursing pigs were cannulated at the terminal ileum and fed the diets described above after weaning at 21 d of age. Ileal samples were collected at 20, 23, 27, 30, 34, 37, and 41 d of age. Samples were assayed for VFA, lactate, and selected microflora. Ileal fermentation acid concentrations and selected microflora were affected by age of pig but were not different between feed treatments. In Exp. 3, 91 21- to 24-d-old weaned pigs were fed the control and test diets already described; intake, BW gain, and feed efficiency were determined for 9 wk after weaning. Intake was greater in pigs fed galactosyl lactose, but ADG and gain/feed did not differ between treatments. Inclusion of galactosyl lactose in weanling pig diets did not affect protein or energy digestibility, microflora, short-chain fatty acids, or performance of young pigs.
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