The morphogenetic switching between yeast cells and filaments (true hyphae and pseudohyphae) is a key cellular feature required for full virulence in many polymorphic fungal pathogens, such as Candida albicans. In the recently emerged yeast pathogen Candida auris, occasional elongation of cells has been reported. However, environmental conditions and genetic triggers for filament formation have remained elusive. Here, we report that induction of DNA damage and perturbation of replication forks by treatment with genotoxins, such as hydroxyurea, methyl methanesulfonate, and the clinically relevant fungistatic 5-fluorocytosine, cause filamentation in C. auris. The filaments formed were characteristic of pseudohyphae and not parallel-sided true hyphae. Pseudohyphal growth is apparently signaled through the S phase checkpoint and, interestingly, is Tup1 independent in C. auris. Intriguingly, the morphogenetic switching capability is strain specific in C. auris, highlighting the heterogenous nature of the species as a whole. IMPORTANCE Candida auris is a newly emerged fungal pathogen of humans. This species was first reported in 2009 when it was identified in an ear infection of a patient in Japan. However, despite intense interest in this organism as an often multidrug-resistant fungus, there is little knowledge about its cellular biology. During infection of human patients, fungi are able to change cell shape from ellipsoidal yeast cells to elongated filaments to adapt to various conditions within the host organism. There are different types of filaments, which are triggered by reactions to different cues. Candida auris fails to form filaments when exposed to triggers that stimulate yeast filament morphogenesis in other fungi. Here, we show that it does form filaments when its DNA is damaged. These conditions might arise when Candida auris cells interact with host immune cells or during growth in certain host tissues (kidney or bladder) or during treatment with antifungal drugs.

Candida auris is a newly emerged pathogenic microbe, having been identified as a medically relevant fungus as recently as 2009. It is one of the most drug-resistant yeast species known to date and its emergence and population structure are unusual. Because of its recent emergence, we are largely ignorant about fundamental aspects of its general biology, life cycle, and population dynamics. Here, we report the karyotype variability of 26 C. auris strains representing the four main clades. We demonstrate that all strains are haploid and have a highly plastic karyotype containing five to seven chromosomes, which can undergo marked alterations within a short time frame when the fungus is put under genotoxic, heat, or osmotic stress. No simple correlation was found between karyotype pattern, drug resistance, and clade affiliation indicating that karyotype heterogeneity is rapidly evolving. As with other Candida species, these marked karyotype differences between isolates are likely to have an important impact on pathogenic traits of C. auris.Electronic supplementary materialThe online version of this article (10.1007/s00294-019-00976-w) contains supplementary material, which is available to authorized users.

ATP-binding cassette (ABC) superfamily members have a key role as nutrient importers and exporters in bacteria. However, their role as drug exporters in eukaryotes brought this superfamily member to even greater prominence. The capacity of ABC transporters to efflux a broad spectrum of xenobiotics represents one of the major mechanisms of clinical multidrug resistance in pathogenic fungi including Candida species. Candida auris , a newly emerged multidrug-resistant fungal pathogen of humans, has been responsible for multiple outbreaks of drug-resistant infections in hospitals around the globe. Our study has analyzed the entire complement of ABC superfamily transporters to assess whether these play a major role in drug resistance mechanisms of C. auris . Our bioinformatics analyses identified 28 putative ABC proteins encoded in the genome of the C. auris type-strain CBS 10913T; 20 of which contain transmembrane domains (TMDs). Quantitative real-time PCR confirmed the expression of all 20 TMD transporters, underlining their potential in contributing to the C. auris drug-resistant phenotype. Changes in transcript levels after short-term exposure of drugs and in drug-resistant C. auris isolates suggested their importance in the drug resistance phenotype of this pathogen. CAUR_02725 orthologous to CDR1 , a major multidrug exporter in other yeasts, showed consistently higher expression in multidrug-resistant strains of C. auris . Homologs of other ABC transporter genes, such as CDR4 , CDR6 , and SNQ2 , also displayed raised expression in a sub-set of clinical isolates. Together, our analysis supports the involvement of these transporters in multidrug resistance in C. auris .

No abstract

The genome of the tomato pathogen Fusarium oxysporum f. sp. lycopersici encodes eight different polygalacturonases (PGs): four endoPGs and four exoPGs. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) revealed that endoPGs pg1 and pg5 and exoPGs pgx4 and pgx6 are expressed at significant levels during growth on citrus pectin, polygalacturonic acid or the monomer galacturonic acid, as well as during the infection of tomato plants. The remaining PG genes exhibit low expression levels under all the conditions tested. Secreted PG activity was decreased significantly during growth on pectin in the single deletion mutants lacking either pg1 or pgx6, as well as in the double mutant. Although the single deletion mutants did not display a significant virulence reduction on tomato plants, the Δpg1Δpgx6 double mutant was significantly attenuated in virulence. The combined action of exoPGs and endoPGs is thus essential for plant infection by the vascular wilt fungus F. oxysporum.

The lipolytic profile of Fusarium oxysporum f. sp lycopersici was studied by in silico search and biochemical enzyme activity analyses. Twenty-five structural secreted lipases were predicted based on the conserved pentapeptide Gly-X-Ser-X-Gly-, characteristic of fungal lipases, and secretion signal sequences. Moreover, a predicted lipase regulatory gene was identified in addition to the previously characterized ctf1. The transcription profile of thirteen lipase genes during tomato plant colonization revealed that lip1, lip3, and lip22 were highly induced between 21 and 96 h after inoculation. Deletion mutants in five lipase genes (lip1, lip2, lip3, lip5, and lip22) and in the regulatory genes ctf1 and ctf2 as well as a Δctf1Δctf2 double mutant were generated. Quantitative reverse transcription-polymerase chain reaction expression analyses of structural lipase genes in the Δctf1, Δctf2, and Δctf1Δctf2 mutants indicated the existence of a complex lipase regulation network in F. oxysporum. The reduction of total lipase activity, as well as the severely reduced virulence of the Δctf1, Δctf2, and Δctf1Δctf2 mutants, provides evidence for an important role of the lipolytic system of this fungus in pathogenicity.

Candida auris has recently emerged as a multi-drug resistant fungal pathogen that poses a serious global health threat, especially for patients in hospital intensive care units (ICUs). C. auris can colonize human skin and can spread by physical contact or contaminated surfaces and equipment. Here, we show that the mycoparasitic yeast Saccharomycopsis schoenii efficiently kills both sensitive and multi-drug resistant isolates of C. auris belonging to the same clade, as well as clinical isolates of other pathogenic species of the Candida genus suggesting novel approaches for biocontrol.

Candida auris is a newly emerging pathogenic microbe, having been identified as a medically relevant fungus as recently as 2009. It is the most drug-resistant yeast species known to date and its emergence and population structure are unusual. Because of its recent emergence we are largely ignorant about fundamental aspects of its general biology, life cycle, and population dynamics. Here we report the karyotype variability of 26 C. auris strains representing the four main clades. We demonstrate that all strains are haploid and have a highly plastic karyotype containing five to seven chromosomes, which can undergo marked alterations within a short time-frame when the fungus is put under genotoxic, heat, or osmotic stress. No simple correlation was found between karyotype pattern, drug resistance, and clade affiliation indicating that karyotype heterogeneity is rapidly evolving. As with other Candida species, these marked karyotype differences between isolates are likely to have an important impact on pathogenic traits of C. auris.Introduction 1 A current, major concern in medical mycology is the emergence of the multidrug-resistant 2 pathogen Candida auris. This species was named according to its first identification as an isolate 3 from the ear canal of a Japanese patient in 2009. 1 Since then, it has rapidly become a major 4 healthcare threat with hospital outbreaks occurring worldwide. [2][3][4] Most C. auris isolates also 5 show high levels of resistance to antifungal drugs, including azoles, echinocandins, 5-flucytosine, 6 and polyenes (amphotericin B). 5,6 C. auris is also difficult to eradicate from hospital intensive 7 care wards and as a skin colonizer it can apparently be transmitted from patient to patient. 4 8 Whole genome sequencing (WGS) of C. auris isolates has indicated that there are at least 9 four distinct geographical clades of this species; East Asia (Japan, Korea), South Asia (India, 10 Pakistan), South Africa, and South America (Venezuela). 6 Clades differ by tens of thousands of 11 single nucleotide polymorphisms (SNPs) from each other, however, within each clade isolates 12 are almost indistinguishable from each other on a DNA sequence level. 5-7 This suggests that the 13 C. auris population structure is characterized by distinct and highly variable clades that are 14 distributed worldwide and almost non-variable clonal expansions of a single genotype within 15 individual outbreaks. 3,4 The origin(s) of the strong variability between and the minor variability 16 within clades are currently unknown. 17 Polyploidy, aneuploidy, and gross chromosome rearrangements have been recognized 18 drivers of genetic diversity in pathogenic and non-pathogenic fungi for some time. 8-12 In 19 pathogenic yeasts, such as C. albicans, mechanisms for ploidy shifts and chromosome 20 rearrangements have been described, and their importance for adaptation to environmental 21 stresses and host niches, as well as for developing resistance to antifungal drugs has been 22 identified. 13-17 23Here, we characteri...