What is a Bacterial Colony? See all Posts. Published On: December 15th, Bacterial Colony Definition and Overview A bacterial colony is what you call a group of bacteria derived from the same mother cell. Why Grow Bacterial Colonies? When done manually in a lab, the colony picking protocol is somewhat tedious and looks something like this in a simplified manner: An agar plate is studied to identify a suitably isolated bacterial colony to pick.
Once selected, the colony is picked up using a toothpick, pipette tip or inoculation loop and transferred to a colony picking cell culture medium, which could be liquid or agar.
Medium is then incubated overnight to encourage further bacterial growth. The resulting colonies are then tested to determine if the end goal has been obtained — either the colony successfully produces a product, or a unique bacteria is found with unique therapeutic or other commercial properties.
Go to Top. At first, there were only anaerobic heterotrophic bacteria the primordial atmosphere was virtually oxygen-free. The first autotrophic bacteria, very similar to the current cyanobacteria, appeared approximately 2 billion years ago. Nutrient broth solution, or culture medium, allows a liquid or gel to provide all the nutrients needed for bacteria to grow successfully. These must include carbohydrates for energy, nitrogen for protein synthesis , plus other minerals. Begin typing your search term above and press enter to search.
Press ESC to cancel. Skip to content Home Philosophy What do bacterial colonies look like? Ben Davis July 3, What do bacterial colonies look like? Why do bacterial colonies look different? How many bacterial cells are in a colony? What are the 6 conditions bacteria need to grow? How many bacteria does it take to form a colony? What happens if you incubate bacteria too long?
How do you speed up bacterial growth? How long can you keep bacterial culture? How long do bacterial stabs last? Rhodospirillum swims in a corkscrew manner, by means of its polar flagella. Other spiral-shaped bacteria include the spirochaetes , such as Treponema pallidum which causes syphilis. However spirochaetes have a different type of motility from that of the common spiral bacteria. The Gram reaction. The Gram reaction is named after the Danish physician, Christian Gram, who developed this staining technique in It involves a series of simple steps.
Bacterial cells are dried onto a glass slide and stained with crystal violet, then washed briefly in water. Iodine solution is added so that the iodine forms a complex with crystal violet in the cells. Alcohol or acetone is added to solubilise the crystal violet - iodine complex. The cells are counterstained with safranin, then rinsed and dried for microscopy.
The method separates bacteria into two types. Gram-positive cells retain the crystal violet-iodine complex and thus appear purple shown for Bacillus cereus in the left-hand image below.
Gram-negative cells are decolourised by the alcohol or acetone treatment, but are then stained with safranin so they appear pink shown for Pseudomonas aeruginosa in the right-hand image below. Thus, the essential difference between Gram-positive and Gram-negative cells is their ability to retain the crystal violet-iodine complex when treated with a solvent. Gram-positive bacteria have a relatively thick wall composed of many layers of the polymer peptidoglycan sometimes termed murein.
The thickness of this wall blocks the escape of the crystal violet-iodine complex when the cells are washed with alcohol or acetone. Gram-negative bacteria have only a thin layer of peptidoglycan, surrounded by a thin outer membrane composed of lipopolysaccharide LPS. The region between the peptidoglycan and LPS layers is termed the periplasmic space coloured grey in the figure ; it is a fluid or gel-like zone containing many enzymes and nutrient-carrier proteins.
The crystal violet-iodine complex is easily lost through the LPS and thin peptidoglycan layer when the cells are treated with a solvent. Myxococcus and other fruiting bacteria Biofilms: their development and significance Exopolysaccharides and their commercial roles Proteus vulgaris and clinical diagnostics Bacillus thuringiensis , a commercial insecticide Bacillus popilliae Airborne microorganisms Penicillin and other antibiotics Winogradsky column Thermophilic microorganisms Cyanobacteria and the 'cryptobiotic crust' Nitrogen fixation Biology and Control of Crown gall Agrobacterium tumefaciens.
Bacterial colonies and cell shapes The image below shows a plate of blood agar inoculated by rolling cottonwool swabs over the surface, then it was incubated at 30 o C for 6 days. The image above was obtained by placing an open agar plate face-down on a flat-bed scanner with the scanner lid closed. Below we see the same plate scanned with the lid open.
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