They are very long thin filament-shaped bacteria. These bacteria do not have any characteristic shape unlike all others described above. They can change their shape.
In pure cultures, they can be observed to have different shapes. In the classification of bacteria by staining, differential staining methods gram stain and acid fast stain methods are used. In the gram staining method bacteria are stained as either positive or negative gram cells using a dye-iodine complex which permeat the cell wall of a gram- negative cell but not gram positive bacteria cell as it permit the outflow of the iodine complex during decoloration..
As in acid- fast staining certain bacteria such as the tubercle baccilli resist decoloration with acids. This is how bacteria are classified by staining method. You said in the introduction that bacteria do not have chlorophyll, but that is untrue.
There are still many kinds of free-living photosynthetic bacteria, or cyanobacteria, in existence. But that would be both pedantic and confusing to your readers…. Why coccus is in the shape of cocci? For example, if you have gold nano particles that are round in shape, and you introduce them into the body for certain types of medical therapies, the nano particles are inert. The body does not react to them. But when you introduce rod-shaped gold nano particles into the body, the body reacts quickly and severely.
The rod shape is essentially getting rejected by the body. Nice listing, although there is a serious typo in the section on the size of bacteria. You state that Epulosisicum fishelsoni has a certain size. First, the genus name is Epulopiscium. Second, and more egregious, is that you state the length to be mm. I think your units here should be micro-meters not milli-meters. A method which makes it easy to remember. Thiomargarita namibiensis is a gram-negative coccoid Proteobacterium, found in the ocean sediments of the continental shelf of Namibia.
It is the largest bacterium ever discovered, as a rule 0. Cells of Thiomargarita namibiensis are large enough to be visible to the naked eye. Although the species holds the record for the most massive bacterium, Epulopiscium fishelsoni — previously discovered in the gut of surgeonfish — grows slightly longer, but narrower.
I wish you were my supervisor or lecturer. Very interesting information. But what is Steptobacilli? Is that also part of human microflora, is it pathogenic?? Save my name and email in this browser for the next time I comment. Size of Bacterial Cell The average diameter of spherical bacteria is 0. One group of bacteria, called the Mycoplasmas, have individuals with size much smaller than these dimensions. They measure about 0. They were formerly known as pleuropneumonia-like organisms PPLO.
Mycoplasma gallicepticum, w ith a size of approximately to nm are thought to be the world smallest bacteria. Usually it is 0. Shape of Bacterial Cell The three basic bacterial shapes are coccus spherical , bacillus rod-shaped , and spiral twisted , however pleomorphic bacteria can assume several shapes. Shape of Bacterial Cell Cocci or coccus for a single cell are round cells, sometimes slightly flattened when they are adjacent to one another.
Bacilli or bacillus for a single cell are rod-shaped bacteria. Arrangement of Cocci Cocci 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.
Diplococci The cocci are arranged in pairs. Streptococci The cocci are arranged in chains, as the cells divide in one plane. Examples: Streptococcus pyogenes, Streptococcus agalactiae 3. Tetrads The cocci are arranged in packets of four cells, as the cells divide in two plains. Examples: Aerococcus, Pediococcus and Tetragenococcus 4.
Sarcinae The cocci are arranged in a cuboidal manner, as the cells are formed by regular cell divisions in three planes. Examples: Sarcina ventriculi, Sarcina ureae, etc. Staphylococci The cocci are arranged in grape-like clusters formed by irregular cell divisions in three plains. Diplobacilli Most bacilli appear as single rods. Diplobacilli appear in pairs after division.
An average bacillus is 0. Spirals come in one of three forms , a vibrio, a spirillum, or a spirochete. There are exceptions to the three basic shapes of coccus, bacillus, and spiral. They include sheathed, stalked, filamentous , square, star-shaped, spindle-shaped, lobed, trichome-forming , and pleomorphic bacteria.
Ultrasmall bacteria could fit in a single Escherichia coli have been discovered in groundwater that was passed through a filter with a pore size of 0. They showed an average length of only nanometers nm and an average width of nm. They contain DNA, an average of 42 ribosomes per bacterium, and possessed pili. It is thought that they use these pili to attach to other bacteria from which they scavenge nutrients.
Because the surface to volume ratio is even greater than in more traditional sized bacteria, they might be better designed to take up scarce nutrients from more nutrient-poor environments.
Learning Objectives List the three basic shapes of bacteria. List and describe 5 different arrangements of cocci. Define and give the abbreviation for the metric unit of length termed micrometer and state the average size of a coccus-shaped bacterium and a rod-shaped bacterium. List and describe 2 different arrangements of bacilli.
List and describe 3 different spiral forms of bacteria. The rod or bacillus Bacilli are rod-shaped bacteria. The spiral Spirals come in one of three forms , a vibrio, a spirillum, or a spirochete.
Exceptions to the above shapes There are exceptions to the three basic shapes of coccus, bacillus, and spiral. Ultrasmall Bacteria Ultrasmall bacteria could fit in a single Escherichia coli have been discovered in groundwater that was passed through a filter with a pore size of 0.
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