Development and implementation of multilocus sequence typing to study the diversity of the yeast Kluyveromyces marxianus in Italian cheeses.

Fabrizia Tittarelli,Loughlin Gethins,Giovanna Suzzi,Rosanna Tofalo,Catherine Stanton,John P Morrissey,Luigi Grazia,Javier A Varela,R.P Ross

doi:10.1099/mgen.0.000153

Fabrizia Tittarelli, Loughlin Gethins + Show 7 more

Open Access

https://doi.org/10.1099/mgen.0.000153

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Abstract

The yeast Kluyveromyces marxianus possesses advantageous traits like rapid growth, GRAS (generally regarded as safe) status and thermotolerance that make it very suitable for diverse biotechnological applications. Although physiological studies demonstrate wide phenotypic variation within the species, there is only limited information available on the genetic diversity of K. marxianus. The aim of this work was to develop a multilocus sequence typing (MLST) method for K. marxianus to improve strain classification and selection. Analysis of housekeeping genes in a number of sequenced strains led to the selection of five genes, IPP1, TFC1, GPH1, GSY2 and SGA1, with sufficient polymorphic sites to allow MLST analysis. These loci were sequenced in an additional 76 strains and used to develop the MLST. This revealed wide diversity in the species and separation of the culture collection and wild strains into multiple distinct clades. Two subsets of strains that shared sources of origin were subjected to MLST and split decomposition analysis. The latter revealed evidence of recombination, indicating that this yeast undergoes mating in the wild. A public access web-based portal was established to allow expansion of the database and application of MLST to additional K. marxianus strains. This will aid understanding of the genetic diversity of the yeast and facilitate biotechnological exploitation.

Highlights

Kluyveromyces marxianus is a homothallic yeast that, along with its sister species Kluyveromyces lactis, belongs to the subphylum Saccharomycotina
Some strains are able to utilize lactose as a carbon source but, unlike K. lactis, it can secrete enzymes that degrade inulin, a fructan found in plants such as Jerusalem artichokes and agave [1, 2]
The capacity to assimilate lactose means that K. marxianus is frequently isolated from dairy products, such as fermented milk, yoghurt, kefir, koumiss and cheese, it can be isolated from fermenting fruit and plant material [3,4,5,6,7]

Summary

Introduction

Kluyveromyces marxianus is a homothallic yeast that, along with its sister species Kluyveromyces lactis, belongs to the subphylum Saccharomycotina. Some strains are able to utilize lactose as a carbon source but, unlike K. lactis, it can secrete enzymes that degrade inulin, a fructan found in plants such as Jerusalem artichokes and agave [1, 2].

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