The superior growth of Kluyveromyces marxianus at very low potassium concentrations is enabled by the high-affinity potassium transporter Hak1.

The non-conventional yeast Kluyveromyces marxianus has recently emerged as a promising candidate for many food, environment, and biotechnology applications. This yeast is thermotolerant and has robust growth under many adverse conditions. Here, we show that its ability to grow under potassium-limiting conditions is much better than that of Saccharomyces cerevisiae, suggesting a very efficient and high-affinity potassium uptake system(s) in this species.

Sodium and lithium exert differential effects on the central carbon metabolism of Debaryomyces hansenii through the glyoxylate shunt regulation.

Debaryomyces hansenii is a halotolerant/halophilic yeast usually found in salty environments. The yeast accumulated sodium at high concentrations, which improved growth in salty media. In contrast, lithium was toxic even at low concentrations and its presence prevented cell proliferation.

The second intracellular loop of the yeast Trk1 potassium transporter is involved in regulation of activity, and interaction with 14-3-3 proteins.

Potassium is an essential intracellular ion, and a sufficient intracellular concentration of it is crucial for many processes; therefore it is fundamental for cells to precisely regulate K uptake and efflux through the plasma membrane. The uniporter Trk1 is a key player in K acquisition in yeasts. The gene is expressed at a low and stable level; thus the activity of the transporter needs to be regulated at a posttranslational level.

The nonpathogenic strain of Fusarium oxysporum FO12 induces Fe deficiency responses in cucumber (Cucumis sativus L.) plants.

FO12 strain enhances Fe deficiency responses in cucumber plants, probably through the production of ethylene and NO in the subapical regions of the roots. Rhizosphere microorganisms can elicit induced systemic resistance (ISR) in plants. This type of resistance involves complex mechanisms that confer protection to the plant against pathogen attack.

Exploring Biocontrol of Unwanted Fungi by Autochthonous Strains Isolated from Dry Meat Products.

The exploration of alternatives to the use of chemical preservatives in food is a topic that has attracted great attention. The implementation of regulations associated with the reduction of these elements directly affects the production of cured meat products, with the premise of looking for more “natural” alternatives. From a previously identified collection of 24 strains of Debaryomyces hansenii, isolated from dry meat products of the “Valle de los Pedroches” (Córdoba), a screening was carried out to determine which strains had inhibitory potential against a battery of fungi belonging to the genera Aspergillus, Penicillium, and Candida.

Potassium Transporters.

Potassium is basic for life. All living organisms require high amounts of intracellular potassium, which fulfils multiple functions. To reach efficient potassium homeostasis, eukaryotic cells have developed a complex and tightly regulated system of transporters present both in the plasma membrane and in the membranes of internal organelles that allow correct intracellular potassium content and distribution.

The Potassium Transporter Hak1 in Regulation and Physiological Effects at Limiting Potassium and under Acidic Conditions.

The three families of yeast plasma membrane potassium influx transporters are represented in : Trk, Acu, and Hak proteins. Hak transporters work as K-H symporters, and the genes coding for Hak proteins are transcriptionally activated under potassium limitation. This work shows that mutant cells lacking display a severe growth impairment at limiting potassium concentrations under acidic conditions.

Regulation and activity of CaTrk1, CaAcu1 and CaHak1, the three plasma membrane potassium transporters in Candida albicans.

Wild-type cells of Candida albicans, the most common human fungal pathogen, are able to grow at very low micromolar concentrations of potassium in the external milieu. One of the reasons behind that behaviour is the existence of three different types of K transporters in their plasma membrane: Trk1, Acu1 and Hak1. This work shows that the transporters are very differently regulated at the transcriptional level upon exposure to saline stress, pH alterations or K starvation.

Trk1, the sole potassium-specific transporter in Candida glabrata, contributes to the proper functioning of various cell processes.

Candida glabrata is a haploid yeast that is considered to be an emergent pathogen since it is the second most prevalent cause of candidiasis. Contrary to most yeasts, this species carries only one plasma membrane potassium transporter named CgTrk1. We show in this work that the activity of this transporter is regulated at the posttranslational level, and thus Trk1 contributes to potassium uptake under very different external cation concentrations.

Inoculation with a terroir selected Debaryomyces hansenii strain changes physico-chemical characteristics of Iberian cured pork loin.

Debaryomyces hansenii Lr1, previously isolated from naturally fermented cured pork loin ("lomo embuchado"), was used to inoculate Iberian pork loin under four different conditions. In all cases, specifically inoculated D. hansenii yeasts grew on the surface of the product and affected its physico-chemical and sensory characteristics.