Microbiomes and Viromes in Infection

Microbiomes are collections of microorganisms that occupy various regions of the human body and other living species, including bacteria, fungi, viruses and other microbes. These microorganisms reside in a complex ecosystem and serve vital roles in human health by regulating the immune system, boosting nutrient absorption and preventing harmful bacteria from colonising. There are various microbiomes in the human body, including the gut, skin, mouth and vaginal microbiomes. Each of these microbiomes is made up of a distinct mix of bacteria that perform specialised roles. In recent decades, exploration of the gut microbiome has advanced rapidly towards sequence-based screening and a gnotobiotic model in humans (Kho and Lal 2018). The role of the gut microbial population is unique in terms of host physiological functions, homeostasis of immunity, metabolism, dysfunction in the nervous system, etc. (Braat et al. 2006). The human microbiota varies from 10¹³ to 10¹⁴ microbial cells, and the microbial cell to human cell ratio of 1:1 in the colon, 3.8 × 10¹³ bacteria are estimated to exist (Kho and Lal 2018, Sender et al. 2016). The three major phyla recorded in GI tracts are Firmicules, Bacterioidetes and Actinomycetes (Tap et al. 2009), and their functional expansion has been found to be of 50–100 more genes that influence the host physiology (Hooper and Gordon 2001). The gut microbiome, for example, is vital for digestion and the generation of critical nutrients like vitamin K, whereas the skin microbiome protects the skin against dangerous microbes (Braat et al. 2006, Hooper and Gordon 2001, Kho and Lal 2018, Sender et al. 2016, Tap et al. 2009). Microbiome research has expanded in recent years due to an increased interest and the possible influence of these complex ecosystems on human health. The most important fields of microbiome study are shown in Figure 1.