Isolation, characterization, and genome assembly of Barnettozyma botsteinii sp. nov. and novel strains of Kurtzmaniella quercitrusa isolated from the intestinal tract of the termite Macrotermes bellicosus

Abstract

Bioconversion of hemicelluloses into simpler sugars leads to production of a significant amount of pentose sugars, such as D-xylose. However, efficient utilization of pentoses by conventional yeast production strains remains challenging. Wild yeast strains can provide new industrially relevant characteristics and efficiently utilize pentose sugars. To explore this strategy, we isolated gut-residing yeasts from the termite Macrotermes bellicosus collected in Comoé National Park, Côte d´Ivoire. The yeasts were classified through their ITS/LSU sequence, their genomes were sequenced and annotated. We identified a novel yeast species, which we name Barnettozyma botsteinii sp. nov. 1118T (MycoBank: 833563, CBS 16679T and IBT 710) and two new strains of Kurtzmaniella quercitrusa: var. comoensis (CBS 16678, IBT 709) and var. filamentosus (CBS 16680, IBT 711). The two K. quercitrusa strains grow 15% faster on synthetic glucose medium than Saccharomyces cerevisiae CEN.PKT in acidic conditions (pH = 3.2) and both strains grow on D-xylose as the sole carbon source at a rate of 0.35 h−1. At neutral pH, the yeast form of K. quercitrusa var. filamentosus, but not var. comoensis, switched to filamentous growth in a carbon source dependent manner. Their genomes are 11.0-13.2 Mb in size and contain between 4888 and 5475 predicted genes. Together with closely related species, we did not find any relationship between gene content and ability to grow on xylose. Besides its metabolism, K. quercitrusa var. filamentosus also has a large potential as a production organism, because of its capacity to grow at low pH and to undergo a dimorphic shift.

Barnettozyma menglunensis f.a., sp. nov., a novel yeast species isolated from rotting wood

“…[6] as a guide for taxon selection. Saccharomyces cerevisiae CBS 1171 was selected as an outgroup taxon [6]. Multiple sequence alignment was performed using clustal_x version 1.81 [15].…”

“…Subsequently, Barnettozyma vustinii and Barnettozyma sucrosica have been proposed as part of the genus based on their morphology and phylogenetic placement [2, 3]. The latest incorporations to the genus are Barnettozyma siamensis from Thailand, Barnettozyma xylosiphila and Barnettozyma xylosic a from Indonesia, and Barnettozyma botsteinii from Denmark [4–6]. In addition, four species of the genus Candida , including Candida montana , Candida norvegica , Candida qinlingensis and Candida sanyiensis , are known to be members of the Barnettozyma clade [7].…”

“…For phylogenetic placement of our isolates, we downloaded ITS and LSU D1/D2 ex-type sequences of the most similar species from GenBank, following Arrey et al [6] as a guide for taxon selection. Saccharomyces cerevisiae CBS 1171 was selected as an outgroup taxon [6]. Multiple sequence alignment was performed using clustal_x version 1.81 [15].…”

Wickerhamomyces sinyiensis f.a., sp. nov., a new ascomycetous yeast species in the Wickerhamomyces clade isolated in Taiwan

“…The genus Wickerhamomyces can be isolated from a wide variety of habitats worldwide, including plant material, soil, seawater, insect tunnels, the guts of insect larvae, brined vegetables, and jams [3,6,[11][12][13][14][15][28][29][30][31], indicating that it is highly polyphyletic. Strains of W. sinyiensis EN27S07, EN32S07 and GY11S02 were isolated from soil, and EN7M06 was isolated from the fruiting [14]); 3, Candida quercuum (data from [33]); 4, Wickerhamomyces orientalis (data from [34]).…”

“…The number of novel species clustered into these three new genera has increased rapidly, especially with respect to Cyberlindnera and Wickerhamomyces. Between 2009 and the time of writing, an additional 18 and 12 novel species of Wickerhamomyces and Cyberlindnera, respectively, have been reported [5][6][7][8], and six novel species of Barnettozyma have been reported [9][10][11][12][13]. Members of the genera Wickerhamomyces, Cyberlindnera and Barnettozyma are ubiquitous, are distributed worldwide and have been isolated from a wide variety of habitats, including soil, natural plant-related substrates, insects, birds, fermented or brined vegetables and fruits, water and processed beverages worldwide [3,6,10,14,15].…”