The gut microbiota includes trillions of microorganisms that colonize the human gastrointestinal tract, including bacteria, archaea, viruses, and fungi. This complex ecosystem plays a critical role in maintaining intestinal and systemic health. Most of these microbes inhabit the large intestine, establishing a relatively stable and diverse community that contributes to gut homeostasis through various metabolic, immunological, and protective mechanisms.Dominant bacterial phyla, such as...

Microorganisms colonize various regions of the human body, including the mouth, nasal passages, throat, stomach, intestines, urogenital tract, and skin. The total number of microbial cells is estimated to range from 10¹³ to 10¹⁴—comparable to, or exceeding, the number of human somatic cells. This host–microbiome relationship has led to the conceptualization of humans as supraorganisms, wherein microbial communities perform vital roles in development, immunity, and disease...

The large intestine hosts the most densely populated microbial ecosystem in the human body. This complex community primarily consists of anaerobic bacteria, with Bacillota (formerly Firmicutes) and Bacteroidota (formerly Bacteroidetes) as the predominant groups. The distribution of these microbes varies along different sections of the large intestine, influenced by local environmental factors such as oxygen availability and nutrient composition.The cecum, located at the beginning of the large...

The oral microbiome includes a complex ecosystem comprising over 700 microbial species, identified through genomic sequencing and culture-based analyses to date. This community includes a core microbiome, found universally among individuals, and a variable component influenced by environmental factors such as diet, lifestyle, and host genetics. Site-specific conditions, including oxygen gradients, pH levels, and nutrient availability, determine the spatial distribution of these microorganisms...

Obesity significantly alters the pharmacokinetic processes of drug absorption and distribution, presenting unique challenges in medical treatment. The increased fat tissue and decreased lean muscle in obese individuals can significantly affect how drugs are absorbed into the body and distributed across different tissues. This alteration can lead to variances in the effectiveness and safety of medications, necessitating adjustments in dosing or drug selection for obese patients.One notable...

The gut–brain axis is a bidirectional communication system that connects the gastrointestinal tract and the brain. This interaction is mediated through multiple pathways, including the vagus nerve, hormonal signals, immune responses, and chemical messengers produced by gut microbes.Microbial Contributions to Brain FunctionGut microbiota contributes significantly to brain function by producing neuroactive compounds. These include neuroactive compounds that influence neurotransmitters such as...