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Colonial morphology of various specimens of Pseudomonas aeruginosa, including mucoid types. In microbiology, colonial morphology refers to the visual appearance of bacterial or fungal colonies on an agar plate. Examining colonial morphology is the first step in the identification of an unknown microbe.
In biology, a colony is composed of two or more conspecific individuals living in close association with, or connected to, one another. This association is usually for mutual benefit such as stronger defense or the ability to attack bigger prey. [1] Colonies can form in various shapes and ways depending on the organism involved.
They ferment sugars, producing lactic acid as an end product. Many of these species produce carotenoid pigments, which color their colonies yellow or orange. Staphylococcus aureus is a major human pathogen. It can infect almost any tissue in the body, frequently the skin. It often causes nosocomial (hospital-acquired) infections. [9]
Colonies tend to be cream-colored, but will turn red in the presence of iron in media, most likely as a result of pulcherrimin. [ 6 ] [ 9 ] B. licheniformis is found in a wide variety of environments, but especially in soil and in the feathers of birds, where B. licheniformis degrades β-keratin .
Pseudomonas stutzeri is a Gram-negative soil bacterium that is motile, has a single polar flagellum, and is classified as bacillus, or rod-shaped. [1] [2] While this bacterium was first isolated from human spinal fluid, [3] it has since been found in many different environments due to its various characteristics and metabolic capabilities. [4]
Conventional species identification is based on colony morphology, Gram-staining and biochemical tests. Colonies are small with a narrow zone of alpha hemolysis on blood agar plates. Laboratory smears show Gram-positive rods (though Gram stain has low sensitivity for this microbe).
Initially, identification was based on phenotypic characteristics such as growth temperature, colony morphology, growth medium, carbon sources, gelatin hydrolysis, glucose fermentation, among others. This method allowed identification of A. calcoaceticus–A. baumannii complex by the formation of smooth, rounded, mucoid colonies at 37 °C.
The large, wrinkled colonies look like environmental contaminants, so are often discarded as being of no clinical significance. Colony morphology is very variable and a single strain may display multiple colony types, [17] [18] so inexperienced laboratory staff may mistakenly believe the growth is not pure. The organism grows more slowly than ...