Pichia caribaea, a New Species of Yeast Occurring in Necrotic Tissue of Cacti in the Caribbean Area

Abstract

We describe Pichia caribaea, a new species of yeast which is closely related to P. amethionina. P. caribaea, of which 92 strains were isolated, is heterothallic and occurs in nature in both the haploid state and the diploid state. It produces asci with four hat-shaped spores, which are gradually released upon maturity. P. caribaea occurs in rotting tissue of cereoid and opuntia cacti on various islands in the greater Caribbean area and on coastal land masses surrounding it. It resembles P. amethionina var. pachycereana in its assimilation pattern of carbon compounds but differs in its ability to ferment glucose strongly. The DNAs of P. caribaea and the two described varieties of P. amethionina show about 40% complementarity. The type strain of P. caribaea is strain UCD-FST 81-62 (= ATTC 76713 = CBS 7692).In 1978, Starmer et al. (15) described Pichia amethionina, a naturally occurring auxotroph that has an absolute requirement for organic forms of sulfur, such as the sulfur-containing amino acids L-methionine and L-cysteine. This nonfermentative species is represented by two varieties, P. amethionina var. amethionina and P. amethionina var. pachycereana. The former is commonly recovered from rot pockets in cacti of the subtribe Stenocereinae, whereas the latter has its principal habitat in members of the subtribe Pachycereinae (2, 15). All isolates of these two varieties came from decaying columnar and Opuntia cacti in the North American Sonoran desert, including the Baja California peninsula. The DNA relatedness between the two varieties was determined by Holzschu and Phaff (3), who reported a mean DNA-DNA complementarity value of 64.9% 2 3.2% on the basis of 16 pairwise comparisons, including reverse DNA reassociations. Nearly all strains of P. amethionina var. amethionina lack the ability to utilize D-mannitol for growth and are resistant to triterpene glycosides or digitonin at 25"C, while P. amethionina var. pachycereana is D-mannitol positive and is inhibited by these compounds During two expeditions in 1982 and 1983 to collect yeasts from cactus necroses on various islands in the Caribbean Sea and the Bahamas, we discovered another yeast with an absolute requirement for sulfur-containing amino acids that was similar to P. amethionina var. pachycereana, except that glucose was vigorously fermented. Additional strains with these properties had been isolated by J. W. Fell and later by M. A. Lachance in the Exuma chain in the Bahamas, by Starmer and Phaff (14) on the Gulf of Mexico coast of Texas, and more recently by Starmer et al. (10) in Florida. In the publications cited, these isolates were referred to as P. amethionina var. "7' or "fermentans." As a formal description with a Latin diagnosis was not provided, this name constitutes a nomen nudum.To substantiate the basis for a valid description of this group of isolates, we carried out mating tests and DNA-DNA hybridizations between typical strains of the fermenting isolates and the two varieties of P. amethionina. Mating between the fermenting isolates a...

Phylogenetic relationships among species ofPichia, IssatchenkiaandWilliopsisdetermined from multigene sequence analysis, and the proposal ofBarnettozymagen. nov.,Lindneragen. nov. andWickerhamomycesgen. nov.

“… † Data are from (Phaff et al , 1976, 1987, 1992; Kurtzman et al , 1980a, b; Holzschu et al , 1983; Kurtzman, 1984b, 1991; Shen & Lachance, 1993). …”

Starmera pilosocereana sp. nov., a yeast isolated from necrotic tissue of cacti in a sandy coastal dune ecosystem

“…This result showing a hybridization barrier is consistent with a final stage of speciation and strong reproductive isolation between the two species. The formation of asci with aberrant ascospores has been noted by Phaff et al (1992) in interspecific matings between Starmera amethionina or Starmera pachycereana and Starmera caribaea . When mixed, these species are known to produce ascospores with decreased viability (Starmer et al 1978; Phaff et al , 1992).…”

“…Three cactophilic species of the Starmera clade, Starmera amethionina , Starmera pachycereana and Starmera caribaea , occur in necrotic cactus tissues Kurtzman, 2011). Phaff et al (1992) described Pichia caribaea ( = Starmera caribaea ), a species recovered from necrotic tissue of cacti in the tribe Opuntieae and in columnar cacti of the subtribe Pachycereinae. Isolates of this species were obtained from cacti geographically ranging from southern Texas, USA to Venezuela (Kurtzman, 2011).…”