What is bacteria

Bacteria can use most organic and some inorganic compounds as food, and some can survive extreme conditions. A growing interest in the function of the gut microbiome is shedding new light on the roles bacteria play in human health. A gram of soil typically contains about 40 million bacterial cells. A milliliter of fresh water usually holds about one million bacterial cells. There are many different types of bacteria. One way of classifying them is by shape. There are three basic shapes.

Bacterial cells are different from plant and animal cells. Bacteria are prokaryotes, which means they have no nucleus. Heterotrophic bacteria, or heterotrophs, get their energy through consuming organic carbon.

Most absorb dead organic material, such as decomposing flesh. Some of these parasitic bacteria kill their host, while others help them. Bacteria that use photosynthesis are called photoautotrophs. Some types, for example cyanobacteria, produce oxygen. Others, such as heliobacteria, do not produce oxygen.

Those that use chemosynthesis are known as chemoautotrophs. These bacteria are commonly found in ocean vents and in the roots of legumes, such as alfalfa, clover, peas, beans, lentils, and peanuts. There are bacteria in the stratosphere, between 6 and 30 miles up in the atmosphere, and in the ocean depths, down to 32, feet or 10, meters deep.

Aerobes, or aerobic bacteria, can only grow where there is oxygen. Some types can cause problems for the human environment, such as corrosion, fouling, problems with water clarity, and bad smells.

Anaerobes, or anaerobic bacteria, can only grow where there is no oxygen. In humans, this is mostly in the gastrointestinal tract. They can also cause gas, gangrene , tetanus , botulism , and most dental infections.

Facultative anaerobes, or facultative anaerobic bacteria, can live either with or without oxygen, but they prefer environments where there is oxygen. They are mostly found in soil, water, vegetation and some normal flora of humans and animals. Examples include Salmonella.

Mesophiles, or mesophilic bacteria, are the bacteria responsible for most human infections. This is the temperature of the human body. Examples include Listeria monocytogenes , Pesudomonas maltophilia , Thiobacillus novellus , Staphylococcus aureus , Streptococcus pyrogenes , Streptococcus pneumoniae , Escherichia coli , and Clostridium kluyveri.

In some cases, that environment is your child or some other living being. Some bacteria are good for our bodies — they help keep the digestive system in working order and keep harmful bacteria from moving in.

Some bacteria are used to make medicines and vaccines. But bacteria can cause trouble too, as with cavities , urinary tract infections , ear infections , or strep throat. Antibiotics are used to treat bacterial infections. Viruses are even smaller than bacteria. They aren't even a full cell.

They need to use another cell's structures to reproduce. This means they can't survive unless they're living inside something else such as a person, animal, or plant. Instead their control centre containing the genetic information is contained in a single loop of DNA. Some bacteria have an extra circle of genetic material called a plasmid. The plasmid often contains genes that give the bacterium some advantage over other bacteria. For example it may contain a gene that makes the bacterium resistant to a certain antibiotic.

Bacteria are classified into five groups according to their basic shapes: spherical cocci , rod bacilli , spiral spirilla , comma vibrios or corkscrew spirochaetes. They can exist as single cells, in pairs, chains or clusters. Bacteria are found in every habitat on Earth: soil, rock, oceans and even arctic snow. Some live in or on other organisms including plants and animals including humans. There are approximately 10 times as many bacterial cells as human cells in the human body. A lot of these bacterial cells are found lining the digestive system.

Some bacteria live in the soil or on dead plant matter where they play an important role in the cycling of nutrients. Some types cause food spoilage and crop damage but others are incredibly useful in the production of fermented foods such as yoghurt and soy sauce. Relatively few bacteria are parasites or pathogens that cause disease in animals and plants. Another common bacterium that can be harmful to people is Helicobacter pylori. About half of people carry these bacteria in their stomachs, according to the Mayo Clinic.

Most people never show any ill effects of this infection, but in some cases, the bacteria cause peptic ulcers , or painful sores in the lining of the stomach. It's not entirely clear how the bacteria spread, but risk factors include crowded livi. Bacterial vaginosis is a condition in which anaerobic bacteria bacteria that do not use oxygen in their metabolism overtake Lactobacillus , a type of beneficial bacteria, in the vagina.

Symptoms include vaginal itching, gray or green discharge, a fishy odor and pain during urination, according to the Mayo Clinic. It's not clear what causes bacterial vaginosis, according to the Mayo Clinic. Some people are likely susceptible because their vaginal environment is not as comfortable for the Lactobacillus bacteria that make up a healthy vaginal microflora.

Douching or having sex with a new partner or with multiple sexual partners can be a risk factor, possibly because these activities disrupt the usual bacterial communities in the vagina. Bacteria commonly associated with bacterial vaginosis include Gardnerella vaginalis , Prevotella species, Mobiluncus species and Atopobium vaginae , according to the CDC.

If untreated, bacterial vaginosis is a risk factor for preterm birth and can make a person more susceptible to contracting sexually transmitted infections. Bacterial vaginosis can be treated with antibiotics. Antibiotics are typically used to treat bacterial infections.

However, in recent years, improper and unnecessary use of antibiotics has promoted the spread of several strains of antibiotic-resistant bacteria. In cases of antibiotic resistance, the infectious bacteria are no longer susceptible to previously effective antibiotics.

According to the CDC , at least 2 million people in the U. Christopher Crnich, an infectious-disease physician and hospital epidemiologist at the University of Wisconsin Hospitals and William S. Middleton Memorial Veterans Hospital.

MRSA , for example, is one of the more notorious antibiotic-resistant bacterial strains; it resists methicillin and other antibiotics used to treat Staphylococcus infections, which are acquired primarily through skin contact. MRSA infections occur in health care settings such as hospitals and nursing homes, where it can lead to pneumonia or bloodstream infections.

MRSA also spreads in communities, especially in situations where there is a lot of exposed skin, other physical contact and the use of shared equipment — for example, among athletes, in tattoo parlors, and in day care facilities and schools, according to the CDC. Community-acquired MRSA most often causes serious skin infections. An important facet of combating antibiotic resistance is to be careful about their use.

This article was updated on Oct. Live Science. Jump to: What are bacteria? Structure of bacteria How do bacteria eat and reproduce?