Asexual Reproduction through binary fission. They contain 70S ribosomes. Flagella serves as the locomotory organ. It lacks organelles like mitochondria, lysosomes, plastids, Golgi bodies, endoplasmic reticulum, centrosome, etc. These are environmental decomposers and mineralizers. Bacteria are regarded as microscopic organisms that have the ability to survive in diverse environments.
They could be both beneficial as well as harmful in certain ways. They usually have a simple structure without a nucleus and with a few cell organelles.
The bacteria are generally surrounded by the two protective coverings, mainly the outer cell wall and the inner cell membrane. Some bacteria are also covered with a capsule.
A few of the bacteria like mycoplasma do not possess a cell wall. The short whip-like structures called the pili are the extensions that surround the surface of the bacteria. The long whip-like structures are also present on the surface called flagella.
They exhibit both autotrophic and heterotrophic modes of nutrition. The autotrophic bacteria are the ones that derive nutrition from the inorganic substances, and they take in the carbon and hydrogen from the atmospheric carbon dioxide, including H 2 , H 2 S, and NH 3.
Structure of Bacteria. Capsule: A slimy capsule is generally present outside the cell wall of a large number of bacteria. This capsule is composed of polysaccharides and nitrogenous substances like amino acids. This slime layer becomes thick to take the shape of a capsule. Cell wall: All the bacterial cells are often covered by a strong, rigid cell wall. The cell wall is present inside the capsule.
Plasma membrane: Each bacterial cell contains a plasma membrane. Bacteria are one-celled organisms that are made of very simple components. They often lack a nucleus and a cell membrane. Bacteria are universal in that they can be found everywhere. They are even some living in the air you breathe. There are some harmful bacteria that can cause illness and disease and there are others that are essential for us to survive. Bacteria help to break down dead matter and also food in our digestive system.
Most organisms in the Monera Kingdom are able to reproduce through a process called fission. As compared to other bacteria, Archaebacteria have a unique cell wall structure which allows them to survive harsh environmental conditions. They can also be found in less extreme environments fresh and ocean waters and soil. According to a variety of studies, a majority of archaeal bacteria have been shown to possess flagella used for motility.
Compared to the flagella found in other bacteria, archaeal flagella have been found to be more similar to type VI pili of bacteria. In general, they have been described as rotating structures with a filament.
Given that a majority of archaea are either chemotactic or phototactic in nature or both , these structures, consisting of preproteins, allow them to move from one point to another in their respective environments. As a result, it has been suggested to contribute to protein stability that allows the organisms to survive.
The flagella of archaea also have the following functions:. Apart from flagella, some of the archaea have been shown to contain structures known as cannulae on their surface. These are hollow tubes consisting of various subunits of glycoprotein. Like several components of the flagella, these structures are also highly resistant to such extreme environmental conditions as heat.
For the most part, cannulae have been identified in newly formed cells. Given that no studies have found these structures to penetrate the cell cytoplasm they have only been shown to enter the periplasmic region of cells , researchers have concluded that by connecting newly formed cells to each other, these structures allow for nutrient and, in some cases, genetic material between the cells. Pili have been identified in many archaea species across the globe. As is the case with flagella , pili of archaea have been shown to be different from those of other bacteria.
Depending on the species, they also play a number of functions ranging from aggregation to motility. For instance, in a study where Sulfolobus cells were exposed to UV light treatment, pili formation allowed for aggregation of the cells before conjugation occurred the transfer of genetic material from a donor to recipient.
While archaea and other bacteria share various characteristics with regards to the plasma membrane, the plasma membrane of archaea has a number of unique characteristics that contribute to their general characteristics.
In archaea, the glycerol linkage between the phospholipid head and side-chain has been shown to be of the L-isomeric form which is different from the D-isomeric form found in other bacteria and eukaryotes. Also, the ether-linkage located between the glycerol and side chain in archaea provide better chemical stability to the membrane of these organisms which also contributes to their overall ability to survive extreme environmental conditions.
With regards to the plasma membrane, some of the other unique characteristics include:. As is the case with other bacteria, the cell wall of archaea also plays an important role in protecting the internal components of the cell from the environment.
In addition, the cell wall also serves to withstand turgor pressure exerted against the plasma membrane. While some archaea lack a cell wall, these structures vary from one species to another depending on their environment. Moreover, they display characteristics that are unique and different from the cell wall of other bacteria. In some of the species, the cell wall has been shown to contain a proteinaceous S-layer.
This, in some species, acts as the sole component of the cell wall. Although they lack peptidoglycan found in bacteria, some archaea possess pseudomurein, which has a similar chemical structure. Also, they contain N-acetylalosaminuronic acid that is linked to the N-acetylglucosamine thus increasing the overall strength of the structure.
Some of the other components of the cell wall in archaea include:. Commonly referred to as "true bacteria" or simply "bacteria", eubacteria is the more complex domain described as a subkingdom in some books of the kingdom Monera. As compared to archaebacteria, members of eubacteria are more common and widely distributed in most habitats water, soil, inside and on extracellular organisms, etc.
As members of the kingdom Monera, eubacteria are prokaryotes and thus do not have membrane-bound organelles. While some species exist as parasites that cause diseases to both plants and animals including human beings , some bacteria are beneficial and are therefore used for food and drug production among many other uses.
Also known as blue-green algae, cyanobacteria contain chlorophyll that allows them to manufacture their own food. As such, they, like plants, are photosynthetic autotrophs. In nature, they may exist as unicellular, colonial, or filamentous in fresh or marine water. However, they can also be found in terrestrial environments where they use water, carbon dioxide, and solar energy to manufacture their own food. While they can manufacture food on their own, some species in this group also form symbiotic relationships with fungi thus forming lichens.
In this mutualistic relationship, the bacteria provides organic nutrients that the fungi require while the fungi provides inorganic material as well as protection to the bacteria. With over 2, species in this division, cyanobacteria come in many shapes and sizes with varying cellular structures. Some of the species produce toxins in water as well as noxious blooms and are thus of significance in water quality management.
Some of the most popular cyanobacteria include:. As such, they obtain energy from the oxidation of inorganic molecules. Heterotrophs are organisms that obtain energy by consuming organic material. Heterotrophic bacteria are abundant in nature with a majority existing as decomposers. As such, they feed on dead plants and animals in their environment thus breaking them down.
This contributes to soil humus that in turn contributes to proper plant development. These types of bacteria are collectively known as saprophytic bacteria.
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