They usually appear singly.Įxamples: Treponema pallidum, Spirillum minus, Chlamydia trachomatis etc. Spirilla are small, curved and coiled in appearance. whereas spirillum is a singular form that represents a single helical-shaped bacterial cell. It is a plural form, which represents a large number of bacteria that possess a helical shape. They can appear either singly or in pairs, groups etc.Įxamples: Lactobacillus sp, Salmonella sp, Escherichia coli etc. Bacilli are small, cylindrical and elongated in appearance. Oppositely, coccus is a singular form representing a single rod-shaped bacterial cell. It is a plural form, which represents a bacterial population possessing a rod shape. They can appear singly or in pairs, chains, groups, clusters etc.Įxamples: Staphylococcus aureus, Streptococcus hominis, Neisseria gonorrhoea etc. Cocci are small, round and slightly flattened in shape. Conversely, coccus is a singular form, which represents a single spherical-shaped bacterial cell. It is a plural form, which represents a large number of bacteria possessing a spherical shape. Generally, there are three common shapes of bacteria, namely, cocci, bacilli and spirilla. The rigid cell wall decides the shape of bacteria. Bacteria can also function as a multicellular population rather than an individual organism. Even though of small size, bacteria can communicate with the other microorganisms through a mechanism called “ Quorum sensing”. Being a prokaryotic cell, the size of bacteria is smaller than the eukaryotic cells like fungi.īecause of bacteria’s small size, their structure becomes more complicated. The largest bacteria known so far is Thiomargarita namibiensis, which measures a size of 0.1-0.75 nm. In the most diverse group of bacteria, mycoplasma is a type of bacteria considered as the smallest organism (measures a size of 0.25 µm). Some bacteria possess a diameter of 80 µm and a length of 600 µm, which we can see through the naked eyes. The spherical shaped bacteria have an average diameter ranging from 0.5-2.0 µm, whereas the rod shaped bacteria have an average diameter of 0.25-1.0 µm. The bacterial size ranges from 0.5-1.0 µm, which you can observe in the highlighted portion of the image below. In this lesson, we will discuss the size range, common shapes and different arrangement of bacteria. There are 10 times more bacteria in our guts than there are cells in our body.Through microscopic observation, we can determine the morphological or physiological characteristics of bacteria based on bacterial shape and arrangement. thermophilus and Bifidobacterium bifidus. Other bacteria found in yoghurt are Lactobacillus acidophilus or casei, Streptococcus salivarius subsp. bulgaricus to produce lactic acid, which acts on milk protein to give yoghurt its texture and its characteristic acidic taste. Yogurt is made from the fermentation of the lactose in milk by the rod-shaped bacteria Lactobacillus delbrueckii subsp. You will be able to see the bacteria even without using the stain.īacteria can be found isolated, in pairs (diplo), in clusters or in threads (strepto), and they can have different shapes like rods (bacilli), sphere (coccus) etc. Bacteria will appear small even at the highest magnification.
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