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Effects of Glucose and Starch on Lactate Production by Newly Isolated Streptococcus bovis S1 from Saanen Goats.

ABSTRACT: When ruminants are fed high-concentrate diets, Streptococcus bovis proliferates rapidly and produces lactate, potentially causing rumen acidosis. Understanding the regulatory mechanisms of the metabolism of this species might help in developing dietary strategies to alleviate rumen acidosis. S. bovis strain S1 was newly isolated from the ruminal fluid of Saanen dairy goats and then used to examine the effects of glucose and starch on bacterial metabolism and gene regulation of the organic acid-producing pathway in cultures at a pH of 6.5. Glucose or starch was added to the culture medium at 1 g/liter, 3 g/liter (close to a normal range in the rumen fluid), or 9 g/liter (excessive level). Lactate was the dominant acid produced during the fermentation, and levels increased with the amount of glucose or starch in a dose-dependent manner (P < 0.001). The production of formate and acetate in the fermentation media fluctuated slightly with the dose but accounted for small fractions of the total acids. The activities of lactate dehydrogenase (LDH) and ?-amylase (?-AMY) increased with the starch dose (P < 0.05), but the ?-AMY activity did not change with the glucose dose. The relative expression levels of the genes ldh, pfl (encoding pyruvate formate lyase), ccpA (encoding catabolite control protein A), and ?-amy were higher at a dose of 9 g/liter than at 1 g/liter (P < 0.05). Expression levels of pfl and ?-amy genes were higher at 3 g/liter than at 1 g/liter (P < 0.05). The fructose 1,6-diphosphate (FDP) concentration tended to increase with the glucose and starch concentrations. In addition, the S. bovis S1 isolate fermented glucose much faster than starch. We conclude that the quantities of glucose and soluble starch had a major effect on lactate production due to the transcriptional regulation of metabolic genes.This work used a newly isolated S. bovis strain S1 from the rumen fluid of Saanen goats and examined the effects of glucose and soluble starch on organic acid patterns, enzyme activity, and expression of genes for in vitro fermentation. It was found that lactate was the dominant product from S. bovis strain S1, and the quantities of both glucose and starch in the medium were highly correlated with lactate production and with the corresponding changes in associated enzymes and genes. Therefore, manipulating the metabolic pathway of S. bovis to alter the dietary level of readily fermentable sugar and carbohydrates may be a strategy to alleviate rumen acidosis.

SUBMITTER: Chen L

PROVIDER: S-EPMC5038034 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Effects of Glucose and Starch on Lactate Production by Newly Isolated Streptococcus bovis S1 from Saanen Goats.

Chen Lianmin L Luo Yang Y Wang Hongrong H Liu Shimin S Shen Yizhao Y Wang Mengzhi M

Applied and environmental microbiology 20160916 19

<h4>Unlabelled</h4>When ruminants are fed high-concentrate diets, Streptococcus bovis proliferates rapidly and produces lactate, potentially causing rumen acidosis. Understanding the regulatory mechanisms of the metabolism of this species might help in developing dietary strategies to alleviate rumen acidosis. S. bovis strain S1 was newly isolated from the ruminal fluid of Saanen dairy goats and then used to examine the effects of glucose and starch on bacterial metabolism and gene regulation of ...[more]

PMID: 27474714

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Project description:1. A transglucosylase has been separated from the alpha-amylase of Streptococcus bovis by chromatography of the cell extract on DEAE-cellulose. 2. The transglucosylase can synthesize higher maltodextrins from maltotriose, but maltose, isomaltose and panose do not function as donors. 3. Iodine-staining polysaccharide may be synthesized from maltotriose provided that glucose is removed. Synthesis from maltohexaose results in dextrins of sufficient chain length to stain with iodine, but again maltodextrins of longer chain length are formed when glucose is removed from the system. 4. The transglucosylase degrades amylose in the presence of a suitable acceptor, transferring one or more glucosyl residues from the non-reducing end of the donor to the non-reducing end of the acceptor. With [(14)C]glucose as acceptor the maltodextrins produced were labelled in the reducing glucose unit only. 5. The acceptor activities of 25 sugars have been compared with that of glucose. Maltose has 50%, methyl alpha-glucoside has 15%, isomaltose and panose each has 8% and sucrose has 6% of the accepting efficiency of glucose. Mannose and sorbose also had detectable activity. With the exception of maltose all these sugars produced a different series of dextrins from that obtained with glucose. 6. It was concluded that S. bovis transglucosylase transfers alpha-(1-->4)-glucosidic linkages in the same manner as D-enzyme, but some differences in specificity distinguish the two enzymes. Unlike D-enzyme, S. bovis transglucosylase can transfer glucosyl units, producing appreciable amounts of maltose both during synthesis from maltotriose and during transfer from amylose to glucose. 7. No evidence was found that the transglucosylase was extracellular. The enzyme is cell-bound, and is released by treatment of the cells with lysozyme and by suspension of the spheroplasts in dilute buffer. 8. The transglucosylase may be responsible for the storage of intracellular iodophilic polysaccharide that occurs when the cells are grown in the presence of suitable carbohydrate sources.

Dataset Information

Effects of Glucose and Starch on Lactate Production by Newly Isolated Streptococcus bovis S1 from Saanen Goats.

Publications

Effects of Glucose and Starch on Lactate Production by Newly Isolated Streptococcus bovis S1 from Saanen Goats.

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