Gene Expression and Biochemical Analysis of Cheese-Ripening Yeasts: Focus on Catabolism of l -Methionine, Lactate, and Lactose

Abstract

ABSTRACT DNA microarrays of 86 genes from the yeasts Debaryomyces hansenii , Kluyveromyces marxianus , and Yarrowia lipolytica were developed to determine which genes were expressed in a medium mimicking a cheese-ripening environment. These genes were selected for potential involvement in lactose/lactate catabolism and the biosynthesis of sulfur-flavored compounds. Hybridization conditions to follow specifically the expression of homologous genes belonging to different species were set up. The microarray was first validated on pure cultures of each yeast; no interspecies cross-hybridization was observed. Expression patterns of targeted genes were studied in pure cultures of each yeast, as well as in coculture, and compared to biochemical data. As expected, a high expression of the LAC genes of K. marxianus was observed. This is a yeast that efficiently degrades lactose. Several lactate dehydrogenase-encoding genes were also expressed essentially in D. hansenii and K. marxianus , which are two efficient deacidifying yeasts in cheese ripening. A set of genes possibly involved in l -methionine catabolism was also used on the array. Y. lipolytica , which efficiently assimilates l -methionine, also exhibited a high expression of the Saccharomyces cerevisiae orthologs BAT2 and ARO8 , which are involved in the l -methionine degradation pathway. Our data provide the first evidence that the use of a multispecies microarray could be a powerful tool to investigate targeted metabolism and possible metabolic interactions between species within microbial cocultures.