Bacilli are also known as rod-shaped bacteria. Bacilli include bacteria such as Escherichia coli and Salmonella.
What are bacilli?
Escherichia coli is known in the human intestinal flora as a supplier of vitamins, especially vitamin K‘s. The bacterium does not normally cause disease. Click to enlarge. Bacilli are rod-shaped bacteria. The term does not include a specific group of bacteria, but refers exclusively to the appearance of the bacteria. Thus, there are many different types of bacteria among bacilli. These include both gram-positive and gram-negative bacteria. Gram-positive bacteria can be stained blue in the so-called Gram stain. Gram-negative bacteria take on a red stain. While Gram-positive bacteria also have an outer cell membrane in addition to a thick peptidoglycan layer of murein, Gram-negative bacilli lack this additional cell wall. The distinction between Gram-positive and Gram-negative bacilli plays a role in the treatment of infectious diseases. Gram-positive bacilli are fought with different antibiotics than Gram-negative bacteria. Unlike cocci, bacilli usually live alone. Gram-positive bacilli include Bacillus, Lactobacillus, Corynebacterium, Listeria, or Propionibacteria. Gram-negative bacilli include Salmonella, Escherichia, Pseudomonas, and Bacteroides.
Occurrence, distribution, and characteristics
The distribution of rod-shaped bacteria varies greatly depending on the species. For example, bacteria such as Escherichia or Lactobacillus live physiologically in the human intestine. They are part of the healthy intestinal flora there and perform various tasks in digestion. Clostridia also live in small quantities in the human intestine. If the site flora is damaged by antibiotic therapy, for example, the Clostridium bacterium spreads and causes severe inflammation. Humans are also the sole reservoir for the rod-shaped bacterium Corynebacterium diphtheriae. The causative agent of diphtheria is transmitted through close contact with infected persons. Some Salmonella species, on the other hand, are found primarily on eggs and in poultry meat. Other Salmonella species, such as Salmonella typhi, on the other hand, are transmitted preferentially by people who are already ill. However, ingestion is also possible through contaminated animal foods.
Significance and function
Some bacilli live in symbiosis with humans. These include, for example, the lactobacilli. They belong to the order of lactic acid bacteria and occur naturally in humans in the intestine and vagina. Lactobacilli process lactose into lactic acid. They belong to the probiotic bacteria. This means that they worsen the living conditions of pathogenic microorganisms with their metabolic products. They provide an acidic environment. However, most bacteria that have a harmful effect on humans prefer an alkaline environment. Thus, lactobacilli prevent the colonization of pathogenic germs in the vagina and intestines. In the gastrointestinal tract, the bacilli produce various nutrients. These include, for example, niacin and folic acid. Escherichia coli is also a rod bacterium that belongs to the physiological intestinal flora of humans. As part of the site flora, it protects the intestinal mucosa from the colonization of harmful bacteria. In addition, coli bacteria metabolize various nutrients, which then serve to nourish the intestinal mucosal cells. Escherichia coli bacteria further act as producers of vitamin K.
Like lactobacilli and Escherichia coli, Bacteroides also belong to the normal flora of the mucous membranes in the gastrointestinal tract. The exact tasks of the bacteria are still unclear. However, it is certain that they act as placeholders. They settle on the intestinal mucosa and thus prevent pathogenic microorganisms from spreading in the intestine.
Diseases and ailments
Some of the bacilli are pathogenic to humans. These include, for example, Corynebacterium diphteriae. It is the causative agent of diphtheria. Responsible for the sometimes severe symptoms of the disease is the diphtheria toxin. It enters the bacterium via the virus prophage beta. This causes fatigue, nausea and vomiting in tonsillitis and diphtheria of the throat. A yellowish-white coating forms on the tonsils, which is accompanied by a foul-sweetish bad breath.Laryngeal diphtheria is dangerous, causing a barking cough, hoarseness and, in severe cases, choking. Listeria can also cause an infectious disease. Listeriosis is caused by the bacterium Listeria monocytogenes. The clinical picture of listeriosis is variable. In immunocompetent individuals, the infection is usually asymptomatic or with mild flu-like symptoms. Immunocompromised individuals may develop meningoencephalitis, peritonitis, or pneumonia. Listeria infection is also associated with risks in pregnant women. The infection can spread to the unborn child and cause an abortion. In the bacilli group of Clostridia, there are several species that can harm humans. One of these is Clostridium botulinum, the causative agent of botulism. Botulism is also known as meat poisoning. It is a life-threatening poisoning caused by the botulinum toxin of Clostridia. The poisoning is usually caused by spoiled meat or cooked vegetables. The botulinum toxin affects the function of the nerves. Patients have blurred and/or double vision, dilated pupils, and difficulty speaking and swallowing. In severe cases, paralysis spreads throughout the body, eventually leading to death by suffocation or cardiac arrest. Another rod-shaped bacterium from the Clostridia family is Clostridium difficile. Clostridium difficile is one of the most common nosocomial pathogens. In healthy people, the bacterium is a harmless intestinal inhabitant. However, when the competing species of physiological intestinal flora are repressed by the administration of antibiotics, Clostridium difficile can proliferate and produce toxins. These can cause pseudomembranous colitis, a life-threatening diarrheal disease.
