Cocci are spherical or slightly oval bacteria that can form chains or groups. They can be beneficial or harmful, and their shape is useful for classification but doesn’t determine behavior. They are small and have a large surface area, making them efficient at absorbing nutrients but also susceptible to harmful substances. They reproduce by forming clusters of cells, and different formations can occur. Some common species include staphylococci and streptococci, which can cause infections. The term “coccus” also has other meanings in biology, such as a type of insect or a single seed.
The word “coccus” has a couple of different meanings in biology, but it most commonly refers to a type of bacteria that is spherical or slightly oval in shape. In this application, the plural term used to describe entire bacterial chains or infections is cocci, while a single coccus bacterium is called a monococcus. There are many different strains and species in this large family. Some benefit life, by helping to maintain cellular balance or ward off other infections, while others can be quite harmful. In most cases the shape of the bacteria is useful for classification and evolutionary purposes, but it doesn’t say much about how it will behave or what it will do. The individual coding and composition of bacteria most commonly dictate these things.
Physical characteristics
Cocci are some of the smallest bacteria in existence. Their diameters typically average 0.5 to 1.0 micrometres, and they usually have the shape of a flat, elongated oval. This shape also gives them the largest surface area in relation to their size, which allows them to more efficiently absorb nutrients from the environment. In many cases this means that the bacteria are more resilient and more likely to survive harsh environments, but sometimes it can also be a downside. A larger surface area can mean that the bacteria are more susceptible to absorbing harmful substances.
Reproduction
When bacteria reproduce, monococci are formed only when a new cell completely divides from the parent cell. Some monococci are usually present in any species of bacteria with this shape, but it is quite common for them to form clusters of two or more cells.
It is often the case in these types of cleavages that there is not complete separation between the parent and newly formed bacterium. This can lead to a couple of different formations, although regardless of the end result it’s important to note that every single cell retains its original spherical shape. The simplest formation is known as a diplococcus, where two cells remain attached to each other. Neisseria is a genus of bacteria that often forms these pairs of cells. Many Neisseria species are found in healthy human throats, but the bacteria that cause meningitis also belong to this genus.
Chains and Large Groups
Cocci bacteria can also form larger groups, including groups of four, eight, ten, or more. Groups of four are known as tetrads, while groups of eight are called sarcinae. Many bacteria that form a group are typically called staphylococci, which is also the name of a specific genus of bacteria that most often form in this arrangement. The formal genus Staphylococcus includes many species commonly found on human skin, as well as some soil-dwelling bacteria. In most cases it also contains Staphylococcus aureus, which can cause staph infections; these strains are also often resistant to antibiotics.
common species
Multiple chains of bacteria are usually called streptococci, and many bacteria that take this form are found in the genus Streptococcus. A good percentage of these strains are normal throat and nose bacteria, but the species that cause pneumonia, strep throat and scarlet fever are also in this group. Enterococcus and Lactococcus species produce lactic acid, a substance needed to create fermented dairy products such as yogurt. Lactococci, in particular, are often used in the dairy industry both to aid the production of dairy products and to aid consumers in their digestion.
Alternative definitions
The word “coccus” also has a couple of other meanings in the scientific realm that aren’t related to bacteria. A group of small, flat, round tropical insects bears the name, for example; these feed primarily on the bark of citrus trees and coffee plants, making them a well-known pest to growers and farmers in many parts of the world. In botany the term can also be applied to a single seed that separates from a multi-lobed or multi-seeded mass, such as a berry or other fruit. Usually these seeds also have the familiar flattened oval shape.
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