Investigation of bacterial composition by culturing techniques is laborious and prone to strong bias, since the growth requirements of many bacteria are still unknown and therefore cannot be provided under laboratory conditions. To overcome these drawbacks, culture-independent molecular methods based on amplification of 16S rRNA genes have been introduced to obtain a better understanding of the intestinal microbiota.
Most DNA-based methods for intestinal microbiota characterisation rely on PCR amplification with broad-range primers at an early stage of the protocol. Even though reference is frequently made to ‘universal primers’ capturing all bacteria, strictly speaking such oligonucleotides do not exist. Therefore, general bacterial analysis based on 16S rDNA sequencing is in most cases at least slightly biased, and in the worst case (primers with poor coverage) it is biased to the extent that no conclusions can be drawn on the composition of the microbial community analysed. Percentage guanine + cytosine (%G+C) profiling is a method that physically fractionates bacterial chromosomes […]
Bacterial lactic acid fermentation is a biological process wherein rapidly fermentable carbohydrates are metabolised by lactic acid bacteria, with lactic acid as a major product. Lactate is the strongest of the common short-chain fatty acids produced by gastrointestinal bacteria and therefore it tends to reduce residual pH more than other acids. During normal conditions, lactate is rapidly absorbed from the intestine or used as a substrate for lactate-utilising bacteria. However, in cases where lactic acid accumulates in lower intestine due to digestive and absorption disorders in the small-intestine, acidosis occurs. This is analogous to lactic acidosis in ruminants and leads […]