Supplementing peptides and B vitamins led to significant presence of lactic acid bacteria and more microbial diversity
Clostridium and Ethanoligenens were the dominant OTUs in the mineral medium enrichment culture (Figure 3). FISH analysis showed a very different result and demonstrated dominance in biovolume ofRuminococcaceae using the Rums278 probe, to which the genus ofEthanoligenens belongs. Only a minor biovolume ofClostridium was detected using the Chis150 probe.Lactobacillus was present as a very minor population (Figure S4) in the mineral medium enrichment. The discrepancy between sequencing results and FISH evaluation shows that complementary observations of the microbial community structure are needed when analysing a microbial community, referred to as the “full cycle rRNA analysis” by Amannet al. (Schleifer et al., 1995).
Lactococcus and Lactobacillus were dominant OTUs in the complex medium enrichment (Figure 3). Their dominance was confirmed by FISH analysis using the Lactococcus4 (Lactococcus ) and Lacto722 (Lactobacillus ) probes. The presence of Megasphaera and minor presence of Clostridium was also confirmed using the Mega-X (Megasphaera ) and the Chis150 (Clostridium ) probes.
The diversity of the obtained microbial community structures using 16S rRNA amplicon sequencing can be calculated using the Shannon index for the observed genera with a presence > 3% of the total OTU’s. For the mineral medium the Shannon index was 0.94 (sample at 32 SRTs) and for the complex medium this was 1.34 (sample taken at 41 SRTs). Thus, more microbial diversity was observed in the complex medium enrichment compared to the mineral medium enrichment on the basis of the number of genera found (Figure 3).