Which yeast species is characterized by a pink color and is germ tube-negative?

The yeast species characterized by a pink color and germ tube-negative is Rhodotorula spp. This is important to note because Rhodotorula is known for its distinct pink to red pigmentation, which can often be observed when the yeast is cultured on specific agar media. The pink coloration is due to the production of carotenoid pigments.

In addition, Rhodotorula spp. do not produce germ tubes, which is a key feature used in the differentiation of certain yeast species. Germ tubes are a type of outgrowth that some yeasts, particularly Candida species, produce under specific conditions when incubated in serum or other media. The absence of germ tube formation can help in identifying Rhodotorula, distinguishing it from other yeasts like Candida albicans and Candida tropicalis, which are germ tube-positive.

The characteristics of Rhodotorula spp. make it a unique organism in microbiology and an important subject of study within the field of mycology, especially when isolating and identifying environmental and clinical yeast isolates.