Bacteria can be defined as a single-celled organism that can thrive in a multitude of environments, even the most extreme ones. From the human gut to the ocean down to soil, they pervade almost all parts of our environment. They are assumed to have existed since 4 billion years ago and are thought to be the first organisms on our planet since some of the oldest fossils are found to have bacteria-like organisms.
Bacteria also play a major role in human health and the new interest in gut microbes has led to a lot of interesting and important information about them. Humans seem to have a complex relationship with bacteria, on one side it is beneficial and helps in digestion, and on another, it can wreak havoc in the gut and diseases like pneumonia and MRSA. While we use bacteria to curdle yogurt, bacteria could also be a cause of harmful neurological conditions.
They are microscopic and have a single cell with a simple internal structure. They are classified as a prokaryotic group of organisms. They do not have a nucleus and their DNA either floats freely in a mass that looks like twisted threads called nucleoid or exists as distinct circular pieces called plasmids. Its cell contains ribosomes which are spherical units in which protein is stored from various amino acids. In most bacteria, there is an inner cell membrane and an outer protective wall forming 2 layers of protection. In some bacteria like mycoplasmas, there is no inner cell membrane and some of them can have a 3rd outer layer known as a capsule.
Bacteria can reproduce rapidly, in the right kind of environment an E Coli bacteria can create colonies of hundreds of bacteria within a couple of hours. Since they have a single cell and there are no male and female versions, they reproduce asexually by creating its carbon copy genetically. There are 2 ways that reproduction happens in Bacteria:
Binary Fission - A single bacterium replicates its DNA and doubles its cellular content in this process to become larger. This bacterium is called the “parent”. This enlarged cell then splits and pushes the extracellular content out in the form of 2 “daughter” bacteria. The rate at which a bacterium reproduces and the timing depends on temperature and amount of nutrients available to it.
DNA Exchange - Not all bacteria are clones of parents and they can acquire new DNA by:
Conjugation - DNA is passed via an extension on the surface in one bacterium to another.
Transformation - Bacteria picks up DNA from its environment
Transduction - If a virus infects a bacterium, it passes DNA of one bacterium to another.
Bacteria are classified based on a few parameters like type of their cell wall, their shape, genetic makeup.
Types of Bacteria Based on Cell Walls – There are 2 types based on this parameter:
Gram-Positive Bacteria – These have a thick cell wall made of several layers of peptidoglycan which do not have an outer membrane. Streptococcus pneumonia is a gram-positive bacterium that causes pneumonia.
Gram-Negative Bacteria – This kind has a thin layer of a cell wall made of peptidoglycan, and has an outer membrane made of lipopolysaccharide.
Kinds of Bacteria Based on Shape – There are mainly 2 categories of bacteria based on their shape:
Round bacteria called cocci.
Cylindrical shaped ones like a capsule known as bacilli.
Their shapes are reflected in their names like Lactobacillus acidophilus which is used in milk curdling. A few bacteria though have different shapes like a square, star, or stalked.
Classification of bacteria based on the mode of nutrition – Bacteria requires carbon, nitrogen, and water in high quantities to survive along with phosphorus, iron, and many other molecules. Based on this they have 2 broad types:
Autotrophic – They use outside sources of energy like light and chemical compounds to make their own food.
Heterotrophic – They take ready-made food from living or dead organic substances.
Bacteria Classification Based on Respiration Mode: How the breakdown of nutrients happens in bacteria by respiration, segregates them into 2 parts:
Aerobic Bacteria – This respiration requires oxygen for breaking down glucose to produce energy.
Anaerobic Bacteria – The energy production due to respiration happens in such bacteria without oxygen.
A good or beneficial bacteria is what promotes healthy functioning of the body by breaking down food and absorbing nutrients. In our body, there are 85% of good and 15% bad bacteria. Bad or “pathogenic” bacteria can make us sick and in the worst case prove to be fatal. In a weak body, the same good bacteria can multiply to a quantity which can wreak havoc in our bodies. Bad bacteria is caused by a plethora of reasons like food, environment, and also stress in our body. Some of the good bacteria are Bifidobacteria which is found in food and supplements and supports the immune system. An example of bad bacteria is STREPTOCOCCUS PYOGENES which causes sore throat and skin rashes. You can combat the dangers of bad bacteria by taking measures like sleeping well, adding vitamins and mineral rich food in your diet, eating probiotics, etc.
1. What is a Capsule?
It is the 3rd protective outermost layer found in some bacteria.
2. What are Flagella and Pilli?
Bacteria surfaces are covered with a whip like extended structures which aid bacteria to move around and attach to a host. The long extensions are called flagella and short ones are pilli.
3. What is the Gram Stain Test?
This test is used to identify bacteria based on their nature of cell walls and is named after scientist Hans Christian Gram who devised this method in 1884.
4. How Do Bacteria Reproduce?
Bacteria multiplies by the process of binary fission, which is asexual. A single bacterium replicates its DNA and doubles its cellular content in this process to become larger. This bacterium is called the “parent”. This enlarged cell then splits and pushes the extracellular content out in the form of 2 “daughter” bacteria. The rate at which a bacterium reproduces and the timing depends on temperature and amount of nutrients available to it.
6. Name 2 Useful and 2 Harmful Bacteria?
Few Useful bacteria are :
Rhizobium – This provides nutrition to the soil for growing plants by supplying ammonia.
Lactobacillus Acidophilus – Used in making curd from milk.
Some Harmful bacteria are:
Salmonellae – This can be passed to humans if food is not cooked properly and causes fever, abdominal pain, diarrhea, and nausea leading to vomiting.
Helicobacter Pylori – It is present in the stomach lining and if it flares up it can cause stomach ulcers.