Name: how gut imbalance affects health
Uploaded: 2026-05-20T13:42:44.188Z
Duration: 1 min 18 s
Channel: JoVE

The gut microbiome is a complex community composed predominantly of beneficial microbes that maintain digestive health, with low levels of opportunistic pathogens that are kept in check under healthy conditions.A disrupted balance causes dysbiosis, a decrease in microbial diversity, and an overgrowth of certain species.Antibiotics can worsen dysbiosis by eliminating helpful microbes and allowing opportunistic pathogens like Clostridioides difficile to overgrow.Over time, dysbiosis reduces the production of microbiota-derived protective metabolites and increases pro-inflammatory signaling, which impairs epithelial tight junctions.This increases intestinal permeability, allowing bacterial components, such as lipopolysaccharides, to enter the bloodstream.Circulating lipopolysaccharides activate innate immune signaling and contribute to systemic low-grade inflammation.They have been associated with increased cardiometabolic risk, based primarily on experimental models and observational human studies.

dysbiosis of the gut microbiota

Dysbiosis of the Gut Microbiota

The human gut microbiome includes a diverse array of microbial species, including beneficial commensals and opportunistic pathogens, which interact to support host health. These microbes contribute to essential functions such as nutrient metabolism, immune system modulation, and maintenance of intestinal barrier integrity. However, disruptions to this equilibrium&#x2014;referred to as dysbiosis&#x2014;can have widespread physiological consequences.Dysbiosis is often characterized by reduced microbial diversity and an imbalance in the relative abundance of major bacterial phyla. Diet significantly influences these microbial dynamics. Diets high in dietary fiber promote the growth of Bacteroidota, which are associated with anti-inflammatory functions and the production of short-chain fatty acids (SCFAs) such as butyrate. These metabolites support colonic health and help regulate immune responses. Conversely, diets rich in fats tend to favor Bacillota, a phylum linked with enhanced energy harvest from food, which may contribute to adiposity.The use of broad-spectrum antibiotics can exacerbate dysbiosis by depleting commensal bacteria, thus enabling opportunistic pathogens such as Clostridioides difficile to proliferate. This pathogen can outcompete residual flora and secrete toxins that further damage the intestinal environment, compounding the disruption.Dysbiosis is implicated in compromising the epithelial barrier of the intestine. Tight junction proteins between epithelial cells become degraded, leading to increased intestinal permeability, commonly referred to as &#x22;leaky gut.&#x22; This permits translocation of bacterial components, notably lipopolysaccharides (LPS), into systemic circulation. Circulating LPS acts as an endotoxin, activating immune cells and adipocytes to secrete pro-inflammatory cytokines and promoting lipid accumulation in arterial walls, thereby increasing the risk for metabolic syndromes, including obesity and atherosclerosis.Long-term microbial imbalance is associated with heightened susceptibility to chronic inflammatory diseases. Inflammatory bowel disease (IBD), including Crohn&#x27;s disease and ulcerative colitis, has been linked to persistent dysbiosis, wherein altered microbial composition perpetuates mucosal inflammation and immune dysregulation. Understanding these relationships is critical for developing microbiome-targeted therapies.

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JoVE Core

Microbiology

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Human Microbiome and Virome

KEY TERMS AND CONCEPTS

how gut imbalance affects health

Gut microbiota imbalance, or dysbiosis, can affect many parts of human health. The gut microbiome includes helpful commensal microbes and opportunistic pathogens that work together to support nutrient metabolism, immune control, and the intestinal barrier. When this balance changes, microbial diversity often drops and the mix of major bacterial groups shifts.

Diet strongly shapes these changes. High-fiber diets support Bacteroidota, which are linked to anti-inflammatory effects and the production of short-chain fatty acids, or SCFAs, such as butyrate. These metabolites help maintain colon health and support immune regulation. Diets high in fats tend to favor Bacillota, a group connected with greater energy harvest from food and possible increases in adiposity.

Broad-spectrum antibiotics can make dysbiosis worse. They reduce commensal bacteria and leave room for opportunistic pathogens such as Clostridioides difficile to grow. This bacterium can outcompete the remaining flora and release toxins that further injure the intestinal environment.

Dysbiosis can also weaken the intestinal epithelial barrier. Tight junction proteins between epithelial cells may break down, which increases intestinal permeability, a condition often called leaky gut. This allows bacterial components, especially lipopolysaccharides (LPS), to enter the bloodstream.

Once in circulation, LPS acts as an endotoxin. It can trigger immune cells and adipocytes to release pro-inflammatory cytokines and can promote lipid buildup in arterial walls. These effects raise the risk of metabolic syndromes, including obesity and atherosclerosis.

Long-term microbial imbalance is also linked to chronic inflammatory disease. Inflammatory bowel disease, or IBD, including Crohn's disease and ulcerative colitis, has been associated with persistent dysbiosis. In these conditions, altered microbes help maintain mucosal inflammation and immune imbalance. Understanding these links is important for microbiome-targeted therapies.

How Gut Imbalance Affects Health

introduction to the human microbiota

How Gut Microbes Support Human Health

Human microbiota are the microorganisms that live on and inside the body. They colonize the mouth, nasal passages, throat, stomach, intestines, urogenital tract, and skin. The total number of microbial cells may range from 10¹³ to 10¹⁴. That means microbes can match or even outnumber human somatic cells. This host-microbiome relationship has led scientists to describe humans as supraorganisms. In this view, microbial communities help shape development, immunity, and disease risk. Studying the...

development of human microbiota

How Early Feeding Shapes the Gut Microbiota

The human microbiota starts forming at birth and changes as a person grows. The first years are a sensitive time for microbial colonization. During this period, helpful microbes support immune system maturity. By about age three, children usually have a more stable and diverse microbial community. Newborns get microbes from the environment around them. Vaginal delivery tends to expose infants to maternal vaginal microbes. Cesarean delivery, or C-section, usually leads to more skin and...

the skin microbiota

How Skin Microbes Protect the Body

The skin hosts bacteria, fungi, and viruses that help protect the body. This microbial community is called the skin microbiome. Its makeup changes from one body region to another because moisture and sebum, the oily skin secretions, differ across the skin surface. Oily areas such as the forehead are often colonized by Cutibacterium acnes. These bacteria break down sebum and make propionic acid. That lowers skin pH and helps create a harsh environment for many harmful microbes. Moist and oily...

microbiome of the eye

Eye Microbiota and Ocular Defense

The eye has a small but specialized microbiota that helps support ocular surface defense. This microbial community is shaped by the eye’s unique anatomy and immune environment. It mostly lives on the conjunctiva and along the eyelid margins. The conjunctival surface carries fewer microbial species than nearby facial skin. Common members include Staphylococcus epidermidis, Cutibacterium acnes, and Corynebacterium species. Blinking helps wash microbes away, and tears add another layer of...

the oral microbiota

Oral Bacteria and Mouth Health

The oral microbiome is a complex community of bacteria and other microbes that live in the mouth. More than 700 microbial species have been identified so far through genomic sequencing and culture-based studies. Some microbes form a core microbiome that is found in most people, while others vary with diet, lifestyle, and host genetics. Different parts of the mouth create different habitats for these microbes. The tongue surface has papillae, or small bumps, that trap food and lower oxygen...

development of the oral microbiota

How Infant Oral Microbes Take Hold

Infant oral microbes begin to take hold before birth and continue to change after delivery. The oral cavity was once thought to be sterile in the fetus, but microbes such as Streptococcus and Fusobacterium have been found in amniotic fluid. This suggests that early microbial exposure may occur in utero through transfer from the maternal oral or gastrointestinal tract. This prenatal exposure may help prime the newborn immune system. Maternal health can also matter, especially if the mother has...

microbiota of the respiratory tract

Respiratory Tract Microbes and Health

The respiratory tract contains microbes that help shape health and disease. It includes the upper respiratory tract, such as the nostrils, sinuses, pharynx, and oropharynx, and the lower respiratory tract, which includes the larynx, trachea, bronchi, and lungs. The upper tract is heavily colonized by microbes, while the lower tract was once thought to be sterile. Recent molecular studies show that the lungs are not microbe-free. Instead, they seem to act as transient reservoirs, meaning...

microbiota of the stomach and small intestine

microbiota-of-the-stomach-and-small-intestine

How Gut Conditions Shape Microbes

Gut conditions shape which microbes can live in the stomach and small intestine. The human gastrointestinal (GI) tract has different physical and chemical settings that affect microbial communities. These settings help explain why some regions hold very few microbes while others support more growth. The stomach is one of the hardest places for microbes to colonize because it is highly acidic. Its pH is usually between 1 and 3, which keeps microbial density low. Even so, some acid-tolerant...

microbiota of the large intestine

Large Intestine Microbes and Their Roles

The large intestine contains the most densely populated microbial ecosystem in the human body. Most of these microbes are anaerobic bacteria, which grow best without oxygen. The main groups are Bacillota, once called Firmicutes, and Bacteroidota, once called Bacteroidetes. Microbes are not spread evenly through the large intestine. Their mix changes from one region to another because oxygen levels and nutrients are different in each area. The cecum, at the start of the large intestine,...

functions of the gut microbiota

Gut Microbiota and Human Health

The gut microbiota is the community of trillions of microorganisms that live in the human gastrointestinal tract. It includes bacteria, archaea, viruses, and fungi. Most of these microbes live in the large intestine, where they form a stable and diverse ecosystem that supports gut homeostasis, or balance. These microbes help break down food components that the body cannot digest on its own. Dominant groups such as Bacteroidota and Bacillota ferment indigestible dietary polysaccharides, which...

Gut microbiota imbalance, or dysbiosis, can affect many parts of human health. The gut microbiome includes helpful commensal microbes and opportunistic pathogens that work together to support nutrient metabolism, immune control, and the intestinal barrier. When this balance changes, microbial diversity often drops and the mix of major bacterial groups shifts. Diet strongly shapes these changes. High-fiber diets support Bacteroidota, which are linked to anti-inflammatory effects and the...

gut-brain axis

Gut Microbes and Brain Health

The gut microbiome helps shape brain health through the gut-brain axis. This bidirectional communication system links the gastrointestinal tract and the brain. It uses the vagus nerve, hormones, immune signals, and chemical messengers made by gut microbes. Gut microbes produce compounds that affect the nervous system. These include neuroactive molecules that can influence neurotransmitters such as serotonin and gamma-aminobutyric acid, or GABA. They also make short-chain fatty acids, including...

microbiota of the urogenital tract

Urogenital Microbiota and Urinary Health

The urogenital tract contains a natural community of microorganisms, and healthy kidneys and bladder are not sterile. Molecular sequencing has shown that these microbes are present even in healthy adults. Their numbers are low compared with the distal urethra, but they still form part of the normal microbial habitat. Most of these resident microbes are harmless, but they can become opportunistic pathogens when the urogenital environment changes. Shifts in pH and disruptions in microbial...

human virome

Human Virome and Body-Site Differences

The human virome is the collection of viruses that live in and on the human body. It includes bacteriophages, which infect bacteria, and eukaryotic viruses, which infect human cells. Viruses from food and the environment can also be part of this shifting community. Estimates suggest the body may contain around 10^13 viral particles, but the number changes by body site and by the method used to detect them. Scientists have learned much more about the virome through untargeted shotgun...

bacteriophages of the human virome

How Bacteriophages Shape Human Microbes

Bacteriophages are viruses that infect bacteria, and they are found throughout the human body. They are a major part of the human virome. In the gut, they can reach very high numbers, and many belong to the orders Caudovirales and Microviridae. A large fraction still cannot be classified and is often described as viral "dark matter." Some bacteriophages integrate their genetic material into bacterial DNA. This process is called lysogeny, and the phage genome then becomes a prophage. During...

microbiota modulation by antibiotics

How Antibiotics Change Gut Bacteria

Antibiotics can change the balance of gut bacteria and other microbes in the human digestive tract. The gut microbiota is a community of bacteria, archaea, viruses, and fungi. It helps control metabolism, immune responses, and intestinal health. Broad-spectrum antibiotics can remove both harmful and helpful microbes and create gut dysbiosis, which means an unbalanced microbiota. These changes can start before birth. Antibiotic use during pregnancy and lactation can alter the mother’s...

key terms and concepts

Learn how dysbiosis, diet, and antibiotics can shift gut microbes, weaken the gut barrier, and raise risks for inflammation and metabolic disease.

How Gut Imbalance Affects Health | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

How Gut Imbalance Affects Health

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