The trichome may in some forms be enclosed in a common sheath.Īpart from the variations of the forms, bacteria may also possess various irregular appearances which are, however, characteristic of a group.
SHAPES OF BACTERIA SHAPES OF BACTERIA SERIES
A trichome consists of a series of cells arranged one on the other to form a column. There are also bacteria which characteristically form filaments or trichomes. Some hyphae enter into the substratum, while others remain in the aerial part. A hypha is an elongated, often branched structure, divided into cells by formation of cross-walls. An actinomycete hypha is about 1 µm in diameter, whereas a fungal hypha is, on the average, 8-10 μm broad. A mycelium is composed of thin hairy hyphae.
A group of prokaryotic organisms, known as actinomycetes, characteristically consist of a mycelium, somewhat like that produced by fungi. Helical bacteria with flexible cells are known as spirochaetes. In all these types, the cell is a rigid structure. If the cylindrical cell is curved, it is known as a vibrio and if helical it is called a spirillum. A spherical bacterium is generally known as a coccus and a cylindrical bacterium, when it is straight, goes under the name of a bacillus.
A cylindrical bacterial cell on losing the wall assumes a spherical shape.Ī bacterium can be spherical or cylindrical. That the cell wall is responsible for giving shape to bacterial cells is also shown when the wall is removed by enzymes. The mycoplasmas are exceptions in this regard, because they lack a cell wall and they do not have also any characteristic shape. Shape of Bacterial Cells :īacterial cells are bound externally by a rigid wall which gives bacteria their characteristic shape. In fact, bacteria are ubiquitous in distribution and they occur in all possible types of environments starting from arctic glaciers to boiling hot springs, and from upper levels of atmospheres to bottom of the seas. The small size also helps bacteria to spread quickly by air currents over great distances. Many bacteria under optimal conditions of growth can have a doubling time of 20 to 30 minutes. This high rate of oxygen uptake reflects the fast rate of metabolic activity of bacteria. Because of a greater surface/volume ratio, the bacteria are able to absorb nutrients and gases from the surrounding media very rapidly and this ability is reflected in their faster growth rate in comparison to larger eukaryotic organisms.įor example, the rate of oxygen uptake (μl/mg dry weight/hr) of most aerobic bacteria is approximately 10 times faster than that of another unicellular but larger organism-yeast-and 100 times faster than the cells of animal tissues. This has important implications on the activity of cells. Due to their small size, bacteria have a much greater surface/volume ratio than most eukaryotic organisms having larger cells. The minute size of bacteria gives certain advantages to them. But such giants among bacteria are extremely rare exceptions. This organism measures 750 μm in diameter and is visible to the unaided eye. For example, a bacterium named Epulopiscium fishelsohnii measuring 80 μm in breadth and 200 μm in length has been discovered in 1991 and another spherical archaebacterium, called Thiomargarita namibiensis has been isolated from sea-bottom in 1999. Some bacteria discovered in recent years, are much larger than the common ones. In general, bacterial cells do not exceed 1 μm (micrometer or micron) in diameter, though their length may vary widely. Individual bacterial cells are not visible to the unaided eye. In this article we will discuss about:-1.
0 kommentar(er)
