DiplococciĮxamples: Streptococcus pneumoniae, Moraxella catarrhalis, Neisseria gonorrhoeae, etc. These group characteristics are often used to help identify certain cocci. Cocci may remain attached after cell division. Cocci may be oval, elongated, or flattened on one side. A special group of spirilla known as spirochetes are long, slender, and flexible.Ĭocci bacteria can exist singly, in pairs (as diplococci ), in groups of four (as tetrads ), in chains (as streptococci ), in clusters (as stapylococci ), or in cubes consisting of eight cells (as sarcinae). Many spirilla are rigid and capable of movement. Spirilla (or spirillum for a single cell) are curved bacteria which can range from a gently curved shape to a corkscrew-like spiral.Bacilli (or bacillus for a single cell) are rod-shaped bacteria.Cocci (or coccus for a single cell) are round cells, sometimes slightly flattened when they are adjacent to one another.The three basic bacterial shapes are coccus (spherical), bacillus (rod-shaped), and spiral (twisted), however pleomorphic bacteria can assume several shapes. One argument favoring this assertion is that even though bacteria have a wide variety of shapes, any one genus typically exhibits a limited subset of morphologies, hinting that, with a universe of shapes to choose from, individual bacteria adopt only those that are adaptive. Thus a few bacteria are much larger than the average eukaryotic cell (typical plant and animal cells are around 10 to 50 µm in diameter). Usually it is 0.1-0.3 mm (100-300 µm) across, but bigger cells have been observed up to 0.75 mm (750 µm). Thiomargarita namibiensis is world’s largest bacteria, a gram-negative Proteobacterium found in the ocean sediments off the coast of Namibia.Mycoplasma gallicepticum, with a size of approximately 200 to 300 nm are thought to be the world smallest bacteria.They were formerly known as pleuropneumonia-like organisms (PPLO). They measure about 0.25 µ and are the smallest cells known so far. One group of bacteria, called the Mycoplasmas, have individuals with size much smaller than these dimensions.The bacterium, Epulosiscium fishelsoni, can be seen with the naked eye (600 µm long by 80 µm in diameter).Oscillatoria is about 7 µm in diameter.Spirochaetes occasionally reach 500 µm in length and the cyanobacterium.coli, a bacillus of about average size is 1.1 to 1.5 µm wide by 2.0 to 6.0 µm long. For rod-shaped or filamentous bacteria, length is 1-10 µm and diameter is 0.25-1. A slime capsule - outside the cell wall, to protect them and stop the bacterium drying out.The average diameter of spherical bacteria is 0.5-2.0 µm.Flagella - tail-like structures that allow bacteria to move through liquids. Many types of bacteria have extra cell structures to help them to survive. Different types of bacteria have different shapes. There are millions of different types of bacteria. Instead, it has a circular strand of DNA, called a plasmid, that floats in the cytoplasm. However unlike most plant and animal cells, it has no nucleus. Bacterium also have a cell wall around them, like plant cells. They all share a cell membrane and cytoplasm. They can exist as single cells, in pairs, chains or clusters. There are similarities between plant and animal cells and a bacterium. Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). So far as the arrangement is concerned, it may Paired (diplo), Grape-like clusters (staphylo) or Chains (strepto). In fact, structure of bacteria has two aspects, arrangement and shape. reproduction - making more living things of the same type major shapes: the rod (bacillus), the sphere (coccus) and the spiral type (vibrio).sensitivity - detecting changes in the surroundings.movement - all living things move, even plants.A single bacterium consists of just one cell, and is called a single-celled, or unicellular organism.Įven though it is just a single cell, it can carry out all seven life processes: Bacteria are among the smallest living things.
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