Which organism is known to produce 'fried-egg' colonies on agar?

The organism that is known to produce 'fried-egg' colonies on agar is Mycoplasma hominis. Mycoplasma species, including M. hominis, are unique among bacteria because they lack a cell wall, which contributes to their distinctive colony morphology. When cultured on agar, they produce colonies that appear flat and have a surface texture reminiscent of a fried egg, with a raised center and a more diffuse edge. This characteristic appearance is a key identifying feature for microbiologists when isolating and identifying Mycoplasma species in laboratory cultures.

In contrast, other organisms mentioned do not exhibit this morphology. For instance, Borrelia burgdorferi, known for causing Lyme disease, requires specialized media and does not produce fried-egg colonies. Similarly, Leptospira interrogans and Treponema pallidum have their own growth characteristics and required conditions that do not lead to the production of fried-egg colonies. Understanding these distinctive features helps in the identification and differentiation of bacterial pathogens in microbial diagnostics.