The types of bacteria prevalent in an environment are determined by several factors. However, bacteria are found in every habitable place on earth. They survive in soil, rocks, oceans, volcanoes, and even arctic snow. Some have been found living in or on other organisms including plants, animals, and humans. The common types of bacteria found in buildings are not harmful when in low numbers. However, just like with mold, elevated levels of bacteria particularly the gram negative type are potentially a health hazard.
Sources and types of bacteria in buildings
Some types of bacteria in buildings are brought in with occupants and with outdoor air. Others are human-gut-associated bacteria such as Lactobacillus, Staphylococcus and Clostridium. These types of bacteria are most common in bathroom environment. Research has shown that the types of bacteria in a building are also influenced by the type of ventilation, i.e., mechanically or naturally ventilated. For example, naturally ventilated buildings are associated with more plant- and soil-associated bacteria while mechanically ventilated buildings are likely to be dominated by human-associated bacteria.
How bacteria survive adverse conditions
Some types of bacteria can form dormant structures called endospores. Endospores are extremely resistant to adverse physical and chemical conditions such as heat, UV radiation and disinfectants. This makes destroying them very difficult. Many endospore-producing bacteria are nasty pathogens, for example Bacillus anthracis, the causal agent of anthrax.
Types of Bacteria based on shape and reaction of their cell walls to certain stains
Bacteria can exist as single cells, in pairs, chains or clusters. They are classified into 5 groups according to their basic shapes:
- spherical: the cocci
- rod: the bacilli
- spiral: the spirilla
- comma: the vibrios or
- corkscrew: the spirochaetes.
On the basis of reaction of their cell walls to certain stains (called Gram staining) bacteria are divided into 2 groups, that is gram positive (bacteria with the cell wall) and gram negative (bacteria without cell wall).
Role of Bacteria in the Environment
Some types of bacteria live in the soil or on dead organic matter where they play an important role in the cycling of nutrients. Some types are harmful and cause food spoilage and crop damage but others are incredibly useful in the production of fermented foods such as yoghurt and soy sauce. There are over 2000 species of bacteria but only a few are parasites or pathogens that cause disease in animals and plants.
Beneficial Types of Bacteria
Not all types of bacteria are harmful. In fact some types are actually helpful to one’s health and their presence may be needed in the body to prevent disease. Examples of beneficial bacteria include:
- Lactobacillus acidophilus. This is a rod-shaped, Gram-positive bacteria normally found in the human intestine, vagina and mouth. They prevent the overgrowth of harmful bacteria in these body parts by producing lactic acid. Due to its beneficial properties, it is used in a variety of dietary products like tempeh, yogurt, miso and probiotics supplements.
- Lactobacillus reuteri. Lactobacillus reuteri is one of the probiotics agents that are present in maternal breast milk and becomes a permanent part of gut flora. It is also present in dietary sources like yogurt and cheese.
- Bifidobacterium animalis. This is a rod-shaped (branched) and Gram-positive bacteria. It aids in digestive process and also prevents diarrhea and yeast infection.
- Escherichia coli. E.coli are rod-shaped, Gram negative bacteria which help to breakdown undigested sugars in the intestine, thus aiding digestion. They also produce biotin and vitamin K which are important to many cellular processes.
- Bacillus subtilis. Bacillus subtilis occurs independently in the environment around us. It helps in normalizing gut motility and metabolic functioning. It is fortified in products like yogurt, cheese, milk, ice cream and fermented soybeans.
- Streptococcus thermophilus. Streptococcus thermophilus has the ability to withstand a temperature of about 100 degrees Celsius. Streptococcus thermophilus strengthen immunity and improves the functioning of gut. It can be obtained from cheese and other dairy products.
Some bacteria found in the environment such Streptomyces, Rhyzobia, and Cyanobacteria inhibit proliferation of harmful bacteria thus maintaining a healthy habitat for man.
Harmful Types of Bacteria
Some of the harmful types of bacteria are those which can cause disease or adversely affect one’s health. These include:
- Mycobacteria. These are rod-shaped, and neither Gram-positive nor Gram-negative bacteria, i.e., they are gram variable. They can cause infections of the lungs, skin and other parts of the body. The most common diseases associated with these bacteria are leprosy and tuberculosis.
- Clostridium tetani. This is a rod-shaped, Gram-positive bacterium that infects the skin and gastrointestinal tract, causing tetanus, which can lead to death.
- Yersinia pestis. This is a rod shaped Gram negative bacterium which infect the skin and lungs. It is the cause of bubonic and pneumonic plague.
- Helicobacter pylori. This is a common type of bacteria associated with gastric and peptic ulcers. Although almost half the world’s population may harbor these harmful bacteria, some do not manifest symptoms.
- Bacillus anthracis. This is a rod-shaped, Gram-positive bacterium which occur in many animals like goats, sheep and cattle but may be transmitted to humans, causing abdominal problems including diarrhea.
- Streptococcus Pyogenes. Streptococcus Pyogenes is a Gram positive coccus. It is the causative agent of mild sore throat and skin infections. In some people these infections may worsen leading to life threatening infections like toxic shock syndrome and septicemia.
- Escherichia coli. E. coli is a gram negative bacillis. It is the causative agent of traveler’s diarrhea.
- Vibrio cholerae. Vibrio cholerae is the causative agent of cholera. The bacterium is acquired through intake of improperly cooked food or poor sanitary conditions.
- Enteritis salmonella. Enteritis salmonella is the most common causative agent of food poisoning throughout the world. It’s presence in food can lead to serious and life threatening food poisoning, diarrhea, circulatory shock
and dehydration in children.
- Salmonella typhi. Salmonella typhi is a gram negative bacterium. It is the causative agent of typhoid fever and may kill if proper treatment is not instituted at the right time. It is associated with a high mortality rate. Symptoms include blood diarrhea, vomiting, dehydration, and fever.
Common Types of Environmental Bacteria
Below are the common types of environmental bacteria. Some are more frequently isolated from the environment than others.
- Acinetobacter spp.
- Alcaligenes spp.
- Bacillus spp.
- Bordetella spp.
- Campylobacter spp.
- Citrobacter spp.
- Clostridium spp.
- Corynebacterium spp.
- Escherichia spp.
- Enterobacter spp.
- Enterococcus spp.
- Flavobacterium spp.
- Klebsiella spp.
- Legionella spp
- Listeria spp.
- Micrococcus spp.
- Mycobacterium spp.
- Nocardia spp.
- Proteus spp.
- Providencia spp.
- Pseudomonas spp.
- Salmonella spp.
- Serratia spp.
- Shigella spp.
- Staphylococcus spp.
- Streptococcus spp.
- Streptomyces spp.
- Thermomonospora spp.
- Yersinia spp.
Other Types of Environmental Bacteria
- Iron bacteria
- Sulphur bacteria