Survival of silage lactic acid bacteria in the goat gastrointestinal tract as determined by denaturing gradient gel electrophoresis

Characterization of two lytic bacteriophages, infecting Streptococcus bovis/equinus complex (SBSEC) from Korean ruminant

Streptococcus bovis/equinus complex (SBSEC) is one of the most important lactic acid-producing rumen bacteria causing subacute ruminal acidosis. Despite the significance of the ruminal bacteria, lytic bacteriophages (phages) capable of infecting SBSEC in the rumen have been rarely characterized. Hence, we describe the biological and genomic characteristics of two lytic phages (designated as vB_SbRt-pBovineB21 and vB_SbRt-pBovineS21) infecting various SBSEC species, including the newly reported S. ruminicola. The isolated SBSEC phages were morphologically similar to Podoviridae and could infect other genera of lactic acid-producing bacteria, including Lactococcus and Lactobacillus. Additionally, they showed high thermal- and pH-stability, and those characteristics induce strong adaptation to the ruminal environment, such as the low pH found in subacute ruminal acidosis. Genome-based phylogeny revealed that both phages were related to Streptococcus phage C1 in the Fischettivirus. However, they had a lower nucleotide similarity and distinct genomic arrangements than phage C1. The phage bacteriolytic activity was evaluated using S. ruminicola, and the phages efficiently inhibited planktonic bacterial growth. Moreover, both phages could prevent bacterial biofilms of various SBSEC strains and other lactic acid-producing bacteria in vitro. Thus, the newly isolated two SBSEC phages were classified as new Fischettivirus members and could be considered as potential biocontrol agents against ruminal SBSEC bacteria and their biofilms.

Study on the bacterial community structure and fermentation characteristics of fresh and ensiled paper mulberry

Two experiments were conducted to investigate the bacterial community of fresh and ensiled paper mulberry prepared with or without lactic acid bacteria (LAB) inoculants in South China. In Experiment 1, the bacterial community, chemical composition, and fermentation products of paper mulberry were analyzed. The results showed that fresh paper mulberry had high crude protein content, buffering capacity value, and amounts of uncultured bacteria. Ensiled paper mulberry showed poor fermentation with high pH value, ammonia-N content, and butyric acid content. In addition, Enterobacter was the dominant genus in silage, followed by Lactobacillus and Enterococcus. Water-soluble carbohydrates, ammonia-N, propionic acid, pH, and lactic acid (LA) were the main factors affecting bacterial community of silage. In Experiment 2, the BP17 (Lactobacillus plantarum) from natural fermented paper mulberry silage and two commercial inoculants (Silage-help [SH] and Chikuso-1 [CH]) were used as additives. Compared with other treatments, BP17 inoculant decreased (p < 0.05) pH and ammonia-N content and increased (p < 0.05) LA content of silage. Inoculation of BP17 also increased the dominance of desirable Lactobacillus and inhibited the growth of harmful bacteria in silage. These results confirmed that paper mulberry could be ensiled and epiphytic LAB inoculant can improve its fermentation quality.

Identification of bacteria in total mixed ration silage produced with and without crop silage as an ingredient

As a forage source for total mixed ration (TMR) silage production, locally produced crop silage is now used in addition to imported hay. This type of TMR ensiling is regarded as a two-step fermentation process; hence, a survey was carried out to determine whether the bacteria in crop silage affect the subsequent TMR ensiling. Fermentation product contents and bacterial community were determined for TMR silage and its ingredient silages collected in August, October and November. August product contained corn, sorghum and Italian ryegrass silages, October product had wheat silage exclusively and November product did not include any crop silages. Acetic acid, lactic acid, 2,3-butanediol and ethanol were predominant fermentation products in corn, sorghum, Italian ryegrass and wheat silages, respectively. Robust lactic acid fermentation was seen in TMR silage, even if acetate-type and alcohol-type silages were mixed as ingredients. The finding that bacterial community of the TMR silage appeared unrelated to those of ingredient silage supported this. Silages of various fermentation types can therefore be formulated without interfering with lactate-type fermentation in TMR silage.