Speaking about viruses that cannot be isolated the same way as bacteria, which leads some people to think that this is a proof that they do not exist... Most of bacteria from our intestines cannot be isolated either!
A typical human intestinal microbiota contains 100–1,000 bacterial species with tremendous compositional diversity between individuals, such that each individual’s microbiota is as unique as a fingerprint. Despite the taxonomic diversity, metagenomic sequencing has highlighted that a health-associated intestinal microbiome codes for highly conserved gene families and pathways associated with basic bacterial physiology and growth. However, many basic microbiota functions related to homeostasis, immune system development, digestion, pathogen resistance and microbiota inheritance have yet to be discovered. This formidable challenge to validate and decipher the functional attributes of the microbiota has been hindered because the majority of intestinal bacteria are widely considered to be ‘unculturable’ and have never been isolated in the laboratory.
Culturing of ‘unculturable’ human microbiota reveals novel taxa and extensive sporulation - Nature
A novel approach is used to cultivate a substantial proportion of the human gut microbiota, representing an important step forward in characterizing the role of these bacteria in health and disease.www.nature.com
The large intestine is a complex microbial ecosystem harbouring more than 500 different bacterial species and around 75% of these remain uncultured (Eckburg et al. 2005; Flint 2006).