yourgogl.blogg.se - Arranged means

The cocci are arranged in packets of four cells, as the cells divide in two plains.Įxamples: Aerococcus, Pediococcus and Tetragenococcus 4. The cocci are arranged in chains, as the cells divide in one plane.Įxamples: Streptococcus pyogenes, Streptococcus agalactiae 3. 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. 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. The average diameter of spherical bacteria is 0.5-2.0 µm. In shape they may principally be Rods (bacilli), Spheres (cocci), and Spirals (spirillum). 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. When viewed under light microscope, most bacteria appear in variations of three major shapes: the rod (bacillus), the sphere (coccus) and the spiral type (vibrio). The cell structure is simpler than that of other organisms as there is no nucleus or membrane bound organelles.ĭue to the presence of a rigid cell wall, bacteria maintain a definite shape, though they vary as shape, size and structure. Bacteria are prokaryotic, unicellular microorganisms, which lack chlorophyll pigments.