Are bacteria necessary for an individual's life, or, how long could a person live without bacteria?

Are bacteria necessary for an individual's life, or, how long could a person live without bacteria?

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Bacteria are essential to life in that they are responsible for breakdown of organic substances, etc. but are bacteria necessary for an individual's life?

In other words, how long would a human survive if they took a super-antibiotic which killed all the bacteria in their body, with the current state of medical technology? If they died what would be the most likely cause of death?

Assume bacteria don't recolonize your body.

Background: I call bacteria the "Lords of the Earth" both to remind myself to be humble and (rather more) as a conversation-starter. I'd like to be able to underline their importance in the ensuing discussions.

You might need to demote your single-celled 'lords' to 'squires'. They're not essential to an individual's life. You wouldn't die (dispensing with the "how" right off the bat.) You'd be just fine if no bacteria reentered your body. Your fecal output would be greater; you would derive somewhat less nutrition from your food, you would need to take vitamin K, and there would be an adjustment period, but theoretically, you'd be just fine. You might even be healthier.

Your hypothetical is impossible, of course, because experimentation on humans is unethical. However, it might surprise you to learn that there are colonies of germ-free animals (also called gnotobiotic) used to study the effect of certain bacteria on animals.

The derivation of such subjects was initially fairly gruesome.

The process of engineering biology and machine began by removing intact uteruses from near- to full-term pregnant animals within a purpose-built germ-free "surgical isolator." The uterus was subsequently passed through various disinfection procedures, involving total immersion in germicide-filled "dunk tanks," before the progeny were surgically released and hand reared within a second microbially sterile isolator.

These animals are costly to keep, as you can imagine. The originals must be delivered by Cesarean section, and housed and raised in sterile conditions. But once you can do that, they can multiply.

To start a germ-free colony, one must remove a young animal from its mother's womb through a careful surgical procedure to avoid exposing it to the microorganisms in the mother's vagina and skin. Then, the animal is raised in a sterile cage and only exposed to food, water, and other equipment that has also been sterilized. On a weekly basis-or more often-a technician swabs cages and animal feces to ensure that no bacteria have contaminated the sterile housing. Once the colony has been created, it becomes easier to rear new germ-free animals; a germ-free mother can give birth naturally without exposing her newborns to any bacteria.

By the 1950s, researchers were rearing germ-free mice, rats, guinea pigs, and chicks inside sterile stainless steel (and later, plastic) housings. Germ-free animals are especially useful in researching, among other things, diabetes, auto-immune diseases, obesity, genetic engineering, cancer, immunology, nutrition, and the effects of normal intestinal flora on health.

Vitamin K must be added to their diets, and it is important to sterilize their food without destroying nutrients, but otherwise they do well in their environments. Their feces, of course, are sterile. Everything is microbe-free. They also have no "normal" antibodies.

Since generations of germ-free animals can exist and multiply, it is not only possible but quite likely that germ-free humans can exist as well.

Which is not to say that gut (and skin, etc.) microbiomes are unimportant. If you release a germ-free animal into a normal environment, it can die if it picks up pathogenic bacteria before more normal gut flora. To do this safely, a germ-free animal is first given a cocktail of bacteria to colonize the gut. After a while, they can be in a normal environment without problems. But your hypothetical human wouldn't even have this problem.

Germ-Free Mice
"Life in a Germ-Free World": Isolating Life from the Laboratory Animal to the Bubble Boy

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Antibiotic resistance

Bacteria are everywhere: in soil, in water, in air, and in the bodies of every person and animal. These microorganisms * are among the most numerous forms of life on Earth.

Most bacteria are either harmless, or helpful, or even essential to life. Bacteria break down (decompose) dead plants and animals. This allows chemical elements like carbon to return to the earth to be used again. In addition, some bacteria help plants get nitrogen. Without them, plants could not grow. In the human body, bacteria help keep the digestive tract working properly.

Like viruses, however, bacteria can cause hundreds of illnesses. Some bacterial infections are common in childhood, such as strep throat and ear infections. Others cause major diseases, such as tuberculosis, plague, syphilis, and cholera. The infection may be localized (limited to a small area), as when a surgical wound gets infected with a bacterium called Staphy loco ccus (staf-i-lo-KOK-us). It may involve an internal organ, as in bacterial pneumonia (infection of the lungs) or bacterial meningitis (infection of the membrane covering the brain and spinal cord).

* microorganisms are living organisms that can only be seen using a microscope. Examples of microorganisms are bacteria, fungi, and viruses.

Some bacteria, such as pneumococcus (noo-mo-KOK-us), which is also called Streptococcus pneumoniae, almost always cause illness if they get into the body. Others, such as Escherichia coli, usually called by the short form E. coli, often are present without doing harm. If the immune system is weakened, however, these bacteria can grow out of control and start doing damage. Such illnesses are called "opportunistic infections." They have become more common in recent years, in part because AIDS, organ transplants, and other medical treatments have left more people living with weakened immune systems.

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How can lowly gut bacteria down there affect higher functions up there in the brain? How can unintelligent, simple organisms affect behaviors, thoughts, and actions of our intellect? These microbiotas have several strategies to affect our brains and therefore minds. One that has already been mentioned above is that gut bacteria produce neurotransmitters that are important for behaviors, mood, thoughts and other cognitive abilities.

Also, some microbiota can change how these brain chemicals get metabolized in the body and thus determine how much is available for action in blood circulation. Other chemicals generated by gut bacteria are called neuroactive, such as butyrate, which has been shown to reduce anxiety and depression. Another pathway is the vagus nerve which is one conduit for the bidirectional gut-brain communication (5). The immune system is yet another one. The immune system is intimately connected to the gut microbiome and the nervous system, and thus can be a mediator of the gut’s effects on the brain and the brain’s effects on the gut.

Not only have many studies across many laboratories showed evidence for brain-gut interactions, but scientists have also cataloged specific bacteria as they relate to various states of mental health. In a large population study (part of the Flemish Gut Flora project), researchers investigated the correlation between microbiome factors and quality of life and depression. Not only did they find a link between the gut microbiome and mental health, but they were able to catalog the exact names of bacteria associated with good and bad quality of life. (6)

What has become evident is that patients with psychiatric disorders have different populations of gut microbes compared to microbes in healthy individuals. Also, stress and stress hormones such as cortisol can have a negative impact on our microbiome. And all of these factors interact in complex ways with the immune system.

As the knowledge of the exact nature of brain-gut interactions unfolds in relation to psychiatric disorders, treatments may include a probiotic instead of Prozac! What all of the above findings strongly suggest is this: Take care of your gut bacteria for good quality of life, better mental health, and a sharper brain.

(1) Sternbach H, State R. Antibiotics: neuropsychiatric effects and psychotropic interactions. (1997). Harv Rev Psychiatry 5: 214–226.

(2) Whitehead WE, Palsson O, Jones KR. Systematic review of the comorbidity of irritable bowel syndrome with other disorders: what are the causes and implications? (2002). Gastroenterology, 122: 1140–1156.

(3) Tillisch, K., Labus, J., Kilpatrick, L., Jiang, Z., Stains, J., Ebrat, B., … Mayer, E. A. (2013). Consumption of fermented milk product with probiotic modulates brain activity. Gastroenterology, 144(7), 1394–1401.e14014. doi:10.1053/j.gastro.2013.02.043

(4) Pearson-Leary, J., Zhao, C., Bittinger, K., …Bhatnagar, S. (2019). The gut microbiome regulates the increase in depressive-type behaviors and in inflammatory processes in the ventral hippocampus of stress vulnerable rats. Molecular Psychiatry.

(5) Bravo, J. A., Forsythe, P., Chew, M.V., …Cryan, J.F. (2011). Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. PNAS, 108(38), 16050-16055.

(6) Valles-Colomer, M., Falony, G., Darzi, Y., . Raes, J. (2019). The neuroactive potential of the human gut microbiota in quality of life and depression. Nature Microbiology, 4, 623-632.

The Main Event &ndash Bacteria in the Digestive System

The human gut is home to a huge range of microorganisms, most of whom enjoy the ideal temperature, acidity level and nutrient supply of the human body. The benefits of bacteria in our digestive system are incredibly important. Without them, we would be unable to digest our food, synthesize certain essential vitamins, absorb water, and fend off the dangerous bacteria that often tries to attack our gut. Some of the most important good gut bacteria include Lactobacilli, Bifidobacterium and Caulobacter. In the stomach and digestive tracts, the most populous pathogenic bacteria include Salmonella, Clostridium, and E. coli. Food poisoning is probably the most common symptom of a bad gut bacteria taking control, but if you have enough beneficial bacteria in your stomach, you should be able to recover quickly.

Good vs. Bad Bacteria (Photo Credit: chombosan / Fotolia)

As mentioned earlier, a significant amount of the immune system also operates out of the gut, making it one of the control centers for our overall health. Keeping the balance between &ldquogood&rdquo and &ldquobad&rdquo microflora in this part of the body is especially important. The beneficial bacteria found in the digestive system are called probiotic bacteria, and there are also a number of foods that contain probiotics to improve your bacterial balance. Probiotics are lactic-acid producing microorganisms that are often used to make certain food products, such as fermented milk, yogurt, kombucha, sauerkraut, miso and soy. If you increase the amount of probiotics in your diet (and gut), you can neutralize harmful bacteria and reduce symptoms of diarrhea, inflammation, nutrient deficiency, cramps, constipation and bloating, as well as more serious stomach conditions and diseases.

How Long Can Viruses Live on Surfaces?

Between all those door handles, credit card keypads and even cell phones, we touch so many surfaces daily. It's just a fact of life. But when it's flu season — or there's an outbreak of any other virus — this simple act of touching stuff can spread germs.

In many cases, it's cause for concern because some viruses can live on surfaces for hours — or even weeks. What's not always clear is how long a surface, like a credit card terminal at the gas pump, might stay contaminated if a sick person sneezes on it.

Part of the uncertainty is because viruses are diverse and have a variety of surface survival rates. There isn't even a hard-and-fast rule for how long a virus can survive outside of a host. The type of surface and environmental temperature and humidity all come into play, too. So which surfaces are safe to touch, and how often do we need to disinfect them?

Before we even discuss how long viruses can live on a surface, we have to understand how viruses work.

No Virus Is an Island

Viruses don't have the right enzymes to create the chemical reactions necessary for reproduction. Instead, viruses need a host cell, which can be bacteria, fungi, a plant or an animal, including a human. With help from the host, viruses are then able to multiply. That's good for the virus but generally bad for the host.

Without the host cell, a virus cannot survive long term however, it does have a short window of time during which it can function in hopes of attaching to (aka infecting) a new host.

Outside its host, a virus can be divided into two categories — either it can be intact and remain infectious or it is simply identifiable, which means it has enough genetic material to be identified but is no longer capable of attaching to host cells, Julia Griffin and Nsikan Akpan wrote in article for PBS News Hour. At the point that a virus on a surface is only identifiable, it won't be able to cause harm.

How Long Can Viruses Live on Surfaces?

The length of time that viruses can live on surfaces and remain infectious varies greatly by pathogen, Dr. Alicia Kraay, postdoctoral fellow in epidemiology at Emory University, explains in an email. There are baseline differences between viruses. For example, rhinovirus — the viruses that cause the common cold — will survive for less than an hour on surfaces. However, others such as the norovirus, which is a virus that can cause vomiting and diarrhea — can survive for weeks. Not surprisingly, with its ability to live this long outside of a host, norovirus can spread both through infected people and through contaminated foods and surfaces.

The research into how long COVID-19 can survive on surfaces is new and ongoing. A March 13 study by researchers at the National Institutes of Health (NIH), the U.S. Centers for Disease Control and Prevention (CDC) and multiple universities compared the novel coronavirus (SARS-CoV-2) with SARS-CoV-1, the most closely related human coronavirus and the virus responsible for the 2003 epidemic. The non-peer-reviewed study found that the two viruses have similar viability in the environment, however, the study determined the novel coronavirus could survive up to three days on stainless steel and plastic surfaces. Survival on other surfaces was lower — just one day on cardboard and four hours on copper. The results indicated that novel coronavirus can live in the air for hours and on surfaces up to days.

Another research study published March 17, 2020, in the New England Journal of Medicine by the National Institute of Allergy and Infectious Diseases and Princeton University also found that the stability of novel coronavirus (SARS-CoV-2) was similar to that of SARS-CoV-1 under the experimental circumstances tested. However, novel coronavirus was more stable than SARS-CoV-1. In their experiments, SARS-CoV-2 remained viable in aerosol form for up to three hours. Viable coronavirus was and detected on plastic and stainless steel up to 72 hours after application. No viable coronavirus was measured after four hours on copper surfaces, and 24 hours on cardboard.

What Factors Affect Virus Survival Rates?

If it seems like it should be a simple test to pinpoint an outside-host survival period, it's more complicated than just spraying some virus on a surface and waiting to see what happens. In fact, in the article for PBS News Hour, Griffin and Akpan wrote that there isn't a lot of "rigorous data" on how long cold and flu viruses remain infectious.

"Generally, survival of pathogens on fomites [objects or materials likely to carry infection] is determined by inoculating a surface with a known quantity of virus and then sampling at various time intervals to determine the amount recovered," Kraay says. "Scientists use this information to estimate a decay curve for the pathogen on the particular surface, which can be extrapolated to longer time intervals."

The NIH and CDC team who studied surface variation for coronavirus is already looking into virus viability in different matrices, as well as in varying environmental conditions.

Although viruses have differing baseline rates of survival on surfaces, additional factors affect their ability to endure outside of a host. Temperature, humidity and surface properties can all affect survival, according to Kraay.

"In general, viruses survive longest at lower temperatures, higher humidity and [on] non-porous surfaces (like stainless steel)," she says. "However, some viruses do well at low humidity."

In addition to surface material and environment, the amount of virus on the surface can also help determine how long it will survive, explains James M. Steckelberg, M.D. in an article for the Mayo Clinic. While it is possible to spread viruses like cold and flu through sharing objects, personal contact is the most common mechanism of spreading viruses.

There have been a lot of theories about whether coronavirus will lessen during warmer months because dry, cold air tends to provide favorable conditions for flu transmission. But Dr. Marc Lipsitch, professor of epidemiology and director, Center for Communicable Diseases Dynamics, Harvard T.H. Chan School of Public Health says when it comes to coronaviruses, the "relevance of this factor is unknown."

Can You Get a Virus From a Surface?

If you touch a surface that is contaminated with a virus — including COVID-19 — does that mean you will get the virus? Not necessarily. But if you don't immediately wash your hands, and then touch your mouth, nose or eyes, you could transmit the virus. However, the CDC says surface contamination isn't considered the most likely way to get coronavirus. Without a host, viruses begin to degrade pretty quickly, so what is on the surface becomes less and less potent.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), explained during the March 13, 2020, CNN/Facebook Global Coronavirus Town Hall that when considering the viability of a virus on various substances, it is probably measured in a couple of hours. While he recommends wiping down surfaces — like doorknobs and cellphone screens — when you can, he cautioned against worrying about money and mail.

In the end, despite the differences in viability on surfaces among pathogens, fomites and contexts, the No. 1 recommendation for preventing the spread of viruses is standard. Wash your hands.

This article was first published on March 16, 2020, and last updated on March 18, 2020.

Thanks to its pH and porous nature, human skin acts as a virus killer for cold and flu viruses — they survive for only about 20 minutes on our hands.


One of the most-prominent differences between bacteria is their requirement for, and response to, atmospheric oxygen (O2). Whereas essentially all eukaryotic organisms require oxygen to thrive, many species of bacteria can grow under anaerobic conditions. Bacteria that require oxygen to grow are called obligate aerobic bacteria. In most cases, these bacteria require oxygen to grow because their methods of energy production and respiration depend on the transfer of electrons to oxygen, which is the final electron acceptor in the electron transport reaction. Obligate aerobes include Bacillus subtilis, Pseudomonas aeruginosa, Mycobacterium tuberculosis, and Acidithiobacillus ferrooxidans.

Bacteria that grow only in the absence of oxygen, such as Clostridium, Bacteroides, and the methane-producing archaea (methanogens), are called obligate anaerobes because their energy-generating metabolic processes are not coupled with the consumption of oxygen. In fact, the presence of oxygen actually poisons some of their key enzymes. Some bacteria (S. pneumoniae) are microaerophilic or aerotolerant anaerobes because they grow better in low concentrations of oxygen. In these bacteria, oxygen often stimulates minor metabolic processes that enhance the major routes of energy production. Facultative anaerobes can change their metabolic processes depending on the presence of oxygen, using the more efficient process of respiration in the presence of oxygen and the less efficient process of fermentation in the absence of oxygen. Examples of facultative anaerobes include E. coli and S. aureus.

The response of bacteria to oxygen is not determined simply by their metabolic needs. Oxygen is a very reactive molecule and forms several toxic by-products, such as superoxide (O2 − ), hydrogen peroxide (H2O2), and the hydroxyl radical (OH · ). Aerobic organisms produce enzymes that detoxify these oxygen products. The most common of detoxifying enzymes are catalase, which breaks down hydrogen peroxide, and superoxide dismutase, which breaks down superoxide. The combined action of these enzymes to remove hydrogen peroxide and superoxide is important because these by-products together with iron form the extremely reactive hydroxyl radical, which is capable of killing the cell. Anaerobic bacteria generally do not produce catalase, and their levels of superoxide dismutase vary in rough proportion with the cell’s sensitivity to oxygen. Many anaerobes are hypersensitive to oxygen, being killed upon short exposure, whereas other anaerobes, including most Clostridium species, are more tolerant to the presence of oxygen.

Can coronavirus be detected on surfaces in healthcare settings?

Coronavirus contamination of surfaces in healthcare settings was studied in Wuhan, China, during the COVID-19 outbreak. Commonly used objects in hospital wards, such as medical equipment and personal protective equipment worn by healthcare workers, were swabbed and tested for virus. [2] Researchers found that the most contaminated zones within the hospital were in the intensive care unit the highest levels of contamination were found on desktops/keyboards (16.8% of total swabs taken were positive), doorknobs (16%), and hand sanitizer dispensers (20.3%). Virus was detected on gloves (15.4%), eye protection and face shields (1.7%). This information gives an indication of where decontamination practises should be focussed to decrease the risk of virus transmission in these settings.


Microbes are the earliest forms of life on earth.1 Biology is difficult enough, but microbiology presents a whole new challenge because it deals with organisms that you can’t even see with the naked eye. To clarify, think of microbiology as biology under a microscope. For us microbiologists, the living world we see without using a microscope is relatively boring compared to the unseen living world at the microscopic level (cf. Colossians 1:16). Bacteria are just one type of organism among many at the microscopic level.2 While diversity of life at the microscopic level is not only bacterial, most scientists generally refer to microbes as bacteria. The importance of referring to microbes with only bacteria in mind is important when describing the microbiome.

The word microbiome comes from the root word microbe. Anytime the letters -ome are added to the end of a word, the meaning of the word changes to mean “all of the” word appearing before it. So the microbiome includes all of the microbes for a given location. While sequencing the human genome was significant, sequencing of the human microbiome could be just as important, since the human body houses 10 bacteria cells for every single human cell. The microbiome is usually measured based on DNA sequencing of the 16S ribosomal subunit to generate what’s called a molecular signature.3 The molecular signature acts like a fingerprint to reveal the bacterial identity.

This image shows common environmental bacteria that are all good for a healthy immune system. It's okay to get dirty, but washing hands after using the bathroom and before eating are good hygiene practices and can prevent disease. Image courtesy of Tasha Sturm, Cabrilo College, via ASM Microbeworld.

Microbiome scientists are interested in questions such as “What bacterial species are present? And in what abundance?” Scientists think of microbiomes like a chef might think of food when planning to cater for a party. Chefs need to know both how many guests there are in addition to what type of food they like. At the microbial level, microbiome scientists measure the human microbiome by considering who is there and how many. The current scientific model of the microbiome follows the Baas-Becking hypothesis that “everything is everywhere, but the environment selects.” Therefore, scientists expect a certain degree of microbiome similarity between similar locations. But the contrast is also true: if two environments are different, then the microbiomes will be different. So how is our microbiome designed?

What Can You Do to Promote Septic Tank Bacteria Growth?

Bacteria will grow naturally in your septic tank. You promote growth of bacteria by flushing more solid waste down into the tank all the time. However, you can do some things to your septic tank that could inhibit growth of bacteria.

Antibacterial soaps, bleach, antibiotics, and other products designed to kill bacteria could all enter your tank and destroy some of the beneficial bacteria in your tank. If you flush these products down your drains on a regular basis, you could significantly disrupt your septic tank's natural processes.

You may need to change the way your household functions in order to avoid flushing these things down the drain. For example, baking soda and vinegar are both excellent bleach alternatives that you can use in household cleaning and laundry.

Soak stained clothes in vinegar before washing them, and add baking soda to your laundry detergent before putting it in the wash. Spray dirty surfaces around the home with vinegar and water.

If you need somewhere to dispose of your medicine safely, talk to your physician to find out where you can get rid of medicines safely. Your physician may know about medicine take-back events in your area.


Microbes in the lower intestinal tract help us digest food, fight harmful bacteria, and regulate the immune system. But sometimes an imbalance of microbes occurs, leading to diarrhea and other health problems.

When the gut becomes unbalanced with unhealthy levels of certain bacteria, probiotics can help restore the balance. They've been shown to secrete protective substances, which may turn on the immune system and prevent pathogens from taking hold and creating major disease. But we are still learning to understand how probiotics may promote health.

Some studies that suggest if you take a probiotic while taking antibiotics, you're less likely to get diarrhea caused by the antibiotic. Probiotics taken as a supplement may also reduce the number of colds you'll have in a year.

Probiotics are commonly used to reduce gastrointestinal symptoms that are not due to acute illness, such as gas, bloating, and constipation. But we need more studies to determine who will get symptom improvement, particularly in older people.

Through Rapid Growth

Bacteria is an organism that is able to grow and divide at a surprisingly rapid rate. Because bacteria is reproduced mostly by asexual reproduction, it can multiply relatively efficiently. Even the growth of bacteria can be increased merely by warmth and moisture. If the conditions are just right, the bacteria will grow and spread quite easily.

Sueanne Dolentz has been writing since 1999, and holds a degree in creative and professional writing. She has worked as a newspaper content editor and humor columnist, as well as a copy writer and website content editor.