Biology subjects

Fernandes, K. E.

Publications and source records attributed to Fernandes, K. E..

3 recordsLinked to original sources

bioRxiv2026

Evidence for fungivory in Proctotydaeus furnarius, a brood mite of the Australian stingless bee Tetragonula carbonaria

Mites are common but poorly understood associates of stingless bee nests. The brood mite Proctotydaeus furnarius inhabits brood cells of Tetragonula carbonaria and was hypothesised to feed on fungi. We tested this hypothesis using electron microscopy, ITS amplicon sequencing, dye-based feeding trials, and brood-cell culturing. The unarmed, needle-like stylets of P. furnarius resembled those of fungivorous mites. In feeding trials, P. furnarius consumed a yeast isolate (Zygosaccharomyces sp.) cultured from brood cells, although also consumed crushed bee pupae. Mite presence did not detectably alter the culturable brood-cell microbial community. These findings suggest that P. furnarius feeds on fungi inside host nests but could shift its diet to feed on host brood according to resource availability.

ecology↗

bioRxiv2022

Lineages derived from Cryptococcus neoformans type strain H99 support a link between the capacity to be pleomorphic and virulence

The pathogenic yeast Cryptococcus neoformans causes nearly 200,000 deaths annually in immunocompromised individuals. Cryptococcus cells can undergo substantial morphological change during mammalian infection, including increased capsule and cell size, the release of shed capsule, and the production of titan (> 10 m), micro (< 2 m) and irregular cells. We examined phenotypic variation under conditions designed to simulate in vivo stress in a collection of nine lineages derived from the C. neoformans type strain H99. These lineages are highly genetically similar but have a range of virulence levels. Strains from hypervirulent lineages had a larger average capsule size, greater variation in cell size, and an increased production of micro cells and shed capsule. We tested whether disruption of SGF29, which encodes a component of the SAGA histone acetylation complex that has previously been implicated in the hypervirulence of some lineages, might also have a role in the production of morphological variants. Deletion of SGF29 in a lineage with intermediate virulence substantially increased its production of micro cells and released capsule, consistent with a switch to hypervirulence. We further examined SGF29 in a set of 52 clinical isolates and found loss-of-function mutations were significantly correlated with patient death. Expansion of a TA repeat in the second intron of SGF29 was positively correlated with cell and capsule size, suggesting it may also affect Sgf29 function. This study extends the evidence for a link between pleomorphism and virulence in Cryptococcus, with a likely role for epigenetic mechanisms mediated by SAGA-induced histone acetylation. IMPORTANCECryptococcosis is a devastating cause of death and disease worldwide. During infection, Cryptococcus cells can undergo substantial changes to their size and shape. In this study, we used a collection C. neoformans strains that are highly genetically similar but possess differing levels of virulence to investigate how morphological variation aligns with virulence. We found hypervirulent strains on average had larger capsules and greater variation in cell size, and also produced more micro cells and shed capsule. These hypervirulent strains possessed a mutation in SGF29, which encodes a component of the SAGA complex involved in epigenetic regulation. Analysis of the SGF29 gene in a set of clinical isolates found strains with loss-of-function mutations were associated with higher patient death rates. The capacity to vary appears to be linked with virulence in Cryptococcus, and this can occur in the absence of genetic variation via epigenetic mechanisms.

microbiology↗

bioRxiv2018

Phenotypic variability correlates with clinical outcome in Cryptococcus isolates obtained from Botswanan HIV/AIDS patients

Pathogenic species of Cryptococcus cause hundreds of thousands of deaths annually. Considerable phenotypic variation is exhibited during infection, including increased capsule size, capsule shedding, giant cells ([≥] 15 m) and micro cells ([≤] 1 m). We examined 70 clinical isolates of Cryptococcus neoformans and Cryptococcus tetragattii from HIV/AIDS patients in Botswana to determine if the capacity to produce morphological variants was associated with clinical parameters. Isolates were cultured under conditions designed to simulate in vivo stresses. Substantial variation was seen across morphological and clinical data. Giant cells were more common in C. tetragattii, while micro cells and shed capsule occurred in C. neoformans only. Phenotypic variables fell into two groups associated with differing symptoms. The production of \"large\" phenotypes (greater cell and capsule size and giant cells) was associated with higher CD4 count and was negatively correlated with intracranial pressure indicators, suggesting these are induced in early-stage infection. \"Small\" phenotypes (micro cells and shed capsule) were associated with lower CD4 counts, negatively correlated with meningeal inflammation indicators and positively correlated with intracranial pressure indicators, suggesting they are produced later during infection and may contribute to immune suppression and promote proliferation and dissemination. These trends persisted at the species level, indicating that they were not driven by association with particular Cryptococcus species. Isolates possessing giant cells, micro cells, and shed capsule were rare, but strikingly were associated with patient death (p=0.0165). Our data indicate that pleomorphism is an important driver in Cryptococcus infection.\n\nImportanceCryptococcosis results in hundreds of thousands of deaths annually, predominantly in sub-Saharan Africa. Cryptococcus is an encapsulated yeast, and during infection cells have the capacity for substantial morphological changes, including capsule enlargement and shedding, and variations in cell shape and size. In this study we examined 70 Cryptococcus isolates causing meningitis in HIV/AIDS patients in Botswana in order to look for associations between phenotypic variation and clinical symptoms. Four variant phenotypes were seen across strains: giant cells [≥] 15 m, micro cells [≤] 1 m, shed extracellular capsule, and irregularly shaped cells. We found \"large\" and \"small\" phenotypes were associated with differing disease symptoms, indicating that their production may be important during the disease process. Overall, our study indicates that Cryptococcus strains that can switch on cell types under different situations may be more able to sustain infection and resist the host response.

microbiology↗