Bacteria are a type of living organism. They are classified as prokaryotes, which are single-celled organisms that lack a nucleus and other organelles. Bacteria are found in every environment on Earth, from the deepest oceans to the inside of animals. There are an estimated 5×1030 bacteria on Earth, making them the most abundant type of organism. Many types of bacteria are beneficial, such as those that help us digest food or produce antibiotics. However, some types of bacteria can cause disease.
Bacteria were first observed by Antonie van Leeuwenhoek in 1676 using a simple microscope he had built himself. He described them as “little animals” that moved around in water. In 1838, Christian Gottfried Ehrenberg proposed the name “bacterium” for these organisms. The word comes from the Greek word βακτήριον (bakterion), meaning “staff” or “rod”, referring to their rod-like shape.
The study of bacteria is known as bacteriology or bacterial ecology. Bacteria can be divided into two main groups: eubacteria and archaebacteria. Eubacteria are more closely related to modern day bacteria, while archaebacteria are more ancient and have unique features not found in eubacteria. Archaebacteria live in extreme environments such as hot springs or salt lakes where other life forms cannot survive.
Most bacteria reproduce by binary fission, where one cell splits into two daughter cells each with an identical copy of the parent’s genetic material (DNA). This process can happen very quickly; some bacteria can double their numbers in as little as 20 minutes! Some types of bacteria also reproduce by forming spores; these are dormant cells that can survive harsh conditions and later germinate into new cells when conditions improve again.
Bacteria generally obtain energy through respiration (using oxygen) or fermentation (without oxygen). Respiration is more efficient but requires oxygen whereas fermentation doesn’t but is less efficient overall so produces less ATP energy molecules per glucose molecule broken down – this is why we get tired after running out of breath during exercise! Photosynthetic bacteria use sunlight to produce their own food like plants do; they convert carbon dioxide into organic matter that can be used for energy just like plants do during photosynthesis . These phototrophic bacteria often live in symbiotic relationships with other organisms such as algae , where they provide each other with nutrients . Chemoautotrophic bacteriaturn harmful chemicals into useful compounds ; for example some sulphur-eating chemoautotrophs oxidise hydrogen sulphide gas released by volcanoes into harmless sulphates which helps fertilise the soil . Lithotrophic bacteriaconsume minerals instead of organic matter ; for example iron-oxidising lithotrophs play an important role in cycles such as the nitrogen cycle where they help convert nitrogen gas into usable nitrates . Some lithotrophs even consume radioactive materials ! There really isn’t any limit to what different kinds