Abstract
The guinea pig (Cavia porcellus) or cavy is a grass-eating rodent. Its main diet consists of grass or hay, which comprises cellulose, hemicellulose, lignin and their derivatives. Here, the microbial diversity of faecal samples of two guinea pigs and microbial enrichments made with substrates, including starch waste and dried grass, were investigated along with organic acid production profiles. The microbial communities of the faecal samples were dominated by the phyla Bacteroidetes (40%) and Firmicutes (36%). Bacteroidales S24-7 (11% in Cavy 1 and 21% in Cavy 2) was the most abundant order. At genus level, many microorganisms remained unclassified. Different carbon sources were used for organic acid production in faecal enrichments. The dominant bacterial groups in the secondary enrichments with dried grass, starch waste and xylose were closely related to Prevotella and Blautia. Acetate was the predominant organic acid from all enrichments. The organic acid production profiles corresponded to a mixed acid fermentation but differed depending on the substrate. Eight phylogenetically different isolates were obtained, including a novel Streptococcus species, strain Cavy grass 6. This strain had a low abundance (1%) in one of the faecal samples but was enriched in the dried grass enrichment (3%). Cavy grass 6, a fast-growing heterolactic bacterium, ferments cellobiose to lactate, acetate, formate and ethanol. Our results show that cavy faecal samples can be applied as microbial source for organic acid production from complex organic substrates. The cavy gut contains many as-yet-uncultivated bacteria which may be appropriate targets for future studies.
Highlights
Guinea pigs (Cavia porcellus) are rodents belonging to the family Caviidae and are native to South America [32]
Blautia was the most abundant operational taxonomic units (OTUs) (41% relative abundance) in the dried grass enrichment, while less than 1% was detected in the starch waste enrichment and it was not detected at all in the xylose enrichment (Fig. 3)
We investigated the microbial community of faecal samples from two domesticated guinea pigs using MiSeq sequencing analysis and found that 68% of the community could not be classified to genus level
Summary
Guinea pigs (Cavia porcellus) are rodents belonging to the family Caviidae and are native to South America [32] They are well known as experimental models for humans and have been used in medical research since the nineteenth century [12]. No research has been performed using guinea pig faecal samples as a source for OA production. The microbial diversity of guinea pig faecal samples was analysed. OA production profiles from cellulose, dried grass, glucose, starch waste, xylan and xylose by guinea pig faecal enrichment cultures were studied. The guinea pig faecal slurry (1% v/v) was used as an inoculum for enrichment with various substrates. Cellulose, dried grass (commercial cavy grass feeding), glucose, soluble starch, starch waste, xylan and xylose (0.5% w/v) were used as carbon sources to selectively enrich bacteria from guinea pig faeces. After 5 days of incubation at 37 °C, the secondary enrichments were used for further analysis
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