Mycobacterium tuberculosis

Tiny germs can live in our lungs.

These germs need air to grow. They have a waxy coat. This coat helps them stay safe. It can even help them live in dry places.

These germs spread through the air. They move when people cough or sneeze. Some germs can even spread when people sing.

Doctors use special tools to find them. It is important to learn about these germs.

Mycobacterium tuberculosis is a tiny germ.

Scientists call it a bacterium. It can cause a sickness called tuberculosis. This germ lives in the lungs of mammals. Humans are the only known ones that carry it.

This bacterium has a very special shell. It has a waxy coating made of lipids. Lipids are fats. This waxy coat helps the germ survive in dry places. It also helps the germ stay safe inside the body. The coat makes it hard for doctors to see the germ with normal stains. Instead, they must use acid-fast stains. These are special dyes that show the germ under a microscope.

These germs spread through the air. They move in tiny droplets. This happens when a sick person coughs or sneezes. It can even happen when they sing or speak.

The germs grow very slowly. Most bacteria divide in minutes. This germ takes about 18 to 24 hours to divide. It can even live for weeks in a dry state.

Mycobacterium tuberculosis is a tiny bacterium that causes tuberculosis.

It is a very special kind of germ. It mostly lives in the lungs of mammals. Humans are actually the only known ones that carry it.

This bacterium is a small, rod-shaped cell. It is very different from many other germs. It can survive for weeks even when it is dry. This makes it a very tough living thing to stop.

This bacterium has a thick, waxy coating on its surface. This coating is made of lipids, which are fats. One important part is called mycolic acid.

This wax acts like a shield for the germ. It helps the bacteria stay safe inside a host. It also makes the germ hard to kill with weak cleaners. Because of this wax, normal dyes do not work well. Scientists must use special acid-fast stains to see them under a microscope.

Robert Koch first discovered this bacterium in 1882.

Since then, scientists have learned much about its life. In 1998, researchers sequenced its entire genome. The genome is like a complete instruction manual for the germ. It is about 4 million base pairs long. It contains 3,959 different genes. Many of these genes help the bacterium use fats for food. This helps it survive during long infections.

Growing this bacterium in a lab is a slow job. Most bacteria divide in just a few minutes. Mycobacterium tuberculosis is much slower than that. It takes about 18 to 24 hours to divide once.

Because it grows so slowly, it can take weeks to see colonies. Scientists use different foods to grow them. They might use egg-based media called Löwenstein-Jensen. They can also use liquid or agar-based media.

The germ spreads through the air in tiny droplets. This happens when a sick person coughs, sneezes, speaks, or even sings.

It does not spread by shaking hands or sharing food. Once inside the lungs, the germ is very clever. It can hide inside immune cells called macrophages. It uses its waxy coat to stop the cell from destroying it. This allows the germ to stay in the body for a long time. This is how it causes a lasting sickness.

Mycobacterium tuberculosis is a species of pathogenic bacteria. It is the specific agent that causes tuberculosis.

This bacterium belongs to the family Mycobacteriaceae. It is a small, rod-shaped bacillus. While many bacteria live in various environments, humans are the only known reservoirs for this specific species. It primarily targets the mammalian respiratory system. Once it enters the lungs, it can cause significant damage to tissue.

The bacterium is famous for its unusual cell surface. It possesses a thick, waxy coating made of lipids. This coating includes mycolic acid and a substance called cord factor glycolipid. This waxy layer acts as a shield. It helps the bacteria resist desiccation, which means drying out. This allows the cells to survive in a dry state for several weeks. The coating also makes the bacteria resistant to weak disinfectants. Because the wax repels most dyes, scientists cannot use a standard Gram stain. Instead, they must use acid-fast stains like Ziehl–Neelsen or fluorescent stains like auramine.

Inside a host, the bacterium uses clever mechanisms to survive. When inhaled, it is swallowed by immune cells called alveolar macrophages. Normally, these cells would digest the germ. However, M. tuberculosis prevents this process. The cord factor glycolipids in the cell wall inhibit the fusion of the phagosome with the lysosome. The lysosome is the part of the cell that contains antibacterial factors. The bacterium also produces a substance called diterpene isotuberculosinol. This prevents the phagosome from maturing. It even secretes a nucleoside called 1-tuberculosinyladenosine to act as an antacid. This helps it neutralize pH levels and induce swelling in lysosomes.

This survival strategy allows the bacteria to stay in a latent state. They find a safe place to replicate inside the host. The body often responds by creating granulomas. These are organized aggregates of immune cells. Granulomas serve a dual purpose. They help regulate the immune response and minimize tissue damage. However, they can also help the infection expand. During an infection, the body may increase levels of a protein called PPM1A. This increase can inhibit apoptotic pathways. Apoptosis is the process where a cell undergoes programmed death to clear a pathogen. By suppressing this, the bacteria maintain a protected niche.

Growing M. tuberculosis in a laboratory requires great patience. Most common bacteria, like Escherichia coli, can divide every 20 minutes. M. tuberculosis is much slower. It divides only once every 18 to 24 hours. Because of this slow rate, visible colonies on agar plates can take several weeks to appear. Scientists use various media to grow them. These include liquid Middlebrook 7H9 or 7H12. They also use egg-based solid media called Löwenstein-Jensen.

Some labs use Mycobacteria Growth Indicator Tubes. These contain a gel that emits fluorescent light if the bacteria are growing.

History has played a major role in our understanding of this pathogen. Robert Koch first discovered the bacterium in 1882. This was a massive breakthrough in microbiology. Later, in 1998, the genome of the H37Rv strain was sequenced. The genome is about 4 million base pairs long. It contains 3,959 genes. Scientists found that 250 of these genes are involved in fatty acid metabolism. This explains how the bacteria use host-derived lipids, like cholesterol, as a food source.

Understanding these genes helps researchers study how the bacteria survive during the chronic phase of infection.

Managing the disease is difficult because of antibiotic resistance. Some strains are considered multidrug-resistant, or MDR TB. This means they are resistant to both rifampicin and isoniazid. The most severe type is extensively drug-resistant, or XDR TB. These strains resist isoniazid, rifampin, a fluoroquinolone, and at least one injectable second-line drug. Resistance happens when mutations accumulate in the bacterial genes. Researchers are looking at ways to target the PPM1A-JNK signaling axis. If they can restore the macrophage's ability to undergo apoptosis, they might improve how chemotherapy works.