We use a 785 nm shifted excitation Raman difference (SERDS) technique to measure the Raman spectra of the conidia of 10 mold species of especial toxicological, medical, and industrial importance, ...including Stachybotrys chartarum, Penicillium chrysogenum, Aspergillus fumigatus, Aspergillus flavus, Aspergillus oryzae, Aspergillus niger, and others. We find that both the pure Raman and fluorescence signals support the hypothesis that for an excitation wavelength of 785 nm the Raman signal originates from the melanin pigments bound within the cell wall of the conidium. In addition, the major features of the pure Raman spectra group into profiles that we hypothesize may be due to differences in the complex melanin biosynthesis pathways. We then combine the Raman spectral data with neural network models to predict species classification with an accuracy above 99%. Finally, the Raman spectral data of all species investigated is made freely available for download and use.
In this work, sequential applications of light-emitting diodes (UV-LEDs) with two wavelengths and chlorine (Cl2) were performed for fungal spores disinfection: UV-Cl2, Cl2-UV, UV/Cl2-UV, UV-UV/Cl2, ...Cl2-UV/Cl2-Cl2. Overall comparisons of the sequential processes with respect to the inhibitory effect on photoreactivation were also evaluated. According to the evaluation of culturability and membrane permeability, inactivation of fungal spores by UV was not enhanced by prior or post exposure to Cl2, but in the UV/Cl2 process with pre or post UV treatment, the inactivation efficiency was greatly enhanced. Take P. polonicum for example, pre-treatments by UV265 and UV280 (40 mJ/cm2) caused the log count reduction (LCR) of 1.05 log and 0.95 log, then the followed UV265/Cl2 and UV280/Cl2 at the same UV fluence caused additional LCR of 1.80 log and 2.00 log. The permeabilization of P. polonicum was also accelerated in the processes of UV/Cl2-UV and UV-UV/Cl2, especially at the wavelength of 280 nm. In the sequential processes, especially those containing UV/Cl2 or at the wavelength of 280 nm, could promote the formation of intracellular reactive oxygen species (ROS), thus leading to more severe damage to the spores as reflected in the culturability reduction, membrane permeability and inhibition of photoreactivation.
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•Inactivation of fungal spores by five types of sequential processes was conducted.•Significant enhanced inactivation was obtained in the processes that contained UV/Cl2.•Enhancement of membrane permeabilization would reduce the VBNC cells.•Novel insights on the combined process of UV-LEDs and chlorine.
Summary
Spore formation is essential for the bacterial pathogen and obligate anaerobe, Clostridioides (Clostridium) difficile, to transmit disease. Completion of this process depends on the mother ...cell engulfing the developing forespore, but little is known about how engulfment occurs in C. difficile. In Bacillus subtilis, engulfment is mediated by a peptidoglycan degradation complex consisting of SpoIID, SpoIIP and SpoIIM, which are all individually required for spore formation. Using genetic analyses, we determined the functions of these engulfment‐related proteins along with the putative endopeptidase, SpoIIQ, during C. difficile sporulation. While SpoIID, SpoIIP and SpoIIQ were critical for engulfment, loss of SpoIIM minimally impacted C. difficile spore formation. Interestingly, a small percentage of ∆spoIID and ∆spoIIQ cells generated heat‐resistant spores through the actions of SpoIIQ and SpoIID, respectively. Loss of SpoIID and SpoIIQ also led to unique morphological phenotypes: asymmetric engulfment and forespore distortions, respectively. Catalytic mutant complementation analyses revealed that these phenotypes depend on the enzymatic activities of SpoIIP and SpoIID, respectively. Lastly, engulfment mutants mislocalized polymerized coat even though the basement layer coat proteins, SpoIVA and SipL, remained associated with the forespore. Collectively, these findings advance our understanding of several stages during infectious C. difficile spore assembly.
Spore formation is essential for the bacterial pathogen Clostridium difficile to transmit disease. A critical step during this process is the engulfment of the developing spore. In Bacillus subtilis, SpoIID, SpoIIPand SpoIIM are essential for engulfment, but we show here that SpoIIM is dispensable for C. difficile spore formation, and SpoIID is only partially required. SpoIID’s enzymatic activity also causes morphological defects in ‘feeding tube’‐mutants. Thus, conserved proteins can have differential functions in spore‐formers.
Moldy food products that are not subject to pathogenic bacterial contamination could be trimmed by consumers to remove fungal mycelium before consumption. However, prior to giving such ...recommendations to consumers, it is necessary to evaluate potential mycotoxin migration in these products. This study aimed at quantifying citrinin (CIT) and ochratoxin A (OTA) accumulation and migration in a French semi-hard Comté cheese after artificial inoculation with a CIT- and OTA-producing Penicillium verrucosum strain. At 8 °C, CIT and OTA production started after 14 days and 28 days incubation, respectively; while at 20 °C, both mycotoxins were produced from day 7. At 20 °C, maximum CIT concentration, about 50000 ng/g, was 20 fold that at 8 °C. Regardless of temperature, maximum OTA concentration was about 4000 ng/g cheese. Maximum concentrations were obtained in the upper part of the cheese, but depending on incubation time, mycotoxins were detected up to 1.6 cm in depth. As long as only white mycelium developed on the cheese surface, trimming can be acceptable, but a blue mold color (due to fungal sporulation) was associated with the accumulation of significant amounts of mycotoxins so the product should be discarded.
•First study to evaluate mycotoxin production and migration in a molded Comté cheese model.•Up to 50 mg/kg CIT at 20 °C, up to 4 mg/kg OTA at 8 and 20 °C.•Blue molded Comté should be discarded because mycotoxins were detected up to 16 mm depth.•The upper 2 mm of moldy cheese can be trimmed as long as white mycelium was observed.•It is recommended to store Comté cheese at low refrigerated temperatures (<8 °C) to slow growth and mycotoxin production.
The biotrophic basidiomycete fungus Ustilago maydis causes smut disease in maize. Hallmarks of the disease are large tumors that develop on all aerial parts of the host in which dark pigmented ...teliospores are formed. We have identified a member of the WOPR family of transcription factors, Ros1, as major regulator of spore formation in U. maydis. ros1 expression is induced only late during infection and hence Ros1 is neither involved in plant colonization of dikaryotic fungal hyphae nor in plant tumor formation. However, during late stages of infection Ros1 is essential for fungal karyogamy, massive proliferation of diploid fungal cells and spore formation. Premature expression of ros1 revealed that Ros1 counteracts the b-dependent filamentation program and induces morphological alterations resembling the early steps of sporogenesis. Transcriptional profiling and ChIP-seq analyses uncovered that Ros1 remodels expression of about 30% of all U. maydis genes with 40% of these being direct targets. In total the expression of 80 transcription factor genes is controlled by Ros1. Four of the upregulated transcription factor genes were deleted and two of the mutants were affected in spore development. A large number of b-dependent genes were differentially regulated by Ros1, suggesting substantial changes in this regulatory cascade that controls filamentation and pathogenic development. Interestingly, 128 genes encoding secreted effectors involved in the establishment of biotrophic development were downregulated by Ros1 while a set of 70 "late effectors" was upregulated. These results indicate that Ros1 is a master regulator of late development in U. maydis and show that the biotrophic interaction during sporogenesis involves a drastic shift in expression of the fungal effectome including the downregulation of effectors that are essential during early stages of infection.
Foliar fungal endophytes are ubiquitous and hyperdiverse, and tend to be host-specific among dominant forest tree species. The fungal genus
Tubakia
sensu lato is comprised of foliar pathogens and ...endophytes that exhibit host preference for
Quercus
and other Fagaceae species. To clarify interspecific differences in ecological characteristics among
Tubakia
species, we examined the endophyte communities of seven evergreen
Quercus
spp. at three sites in eastern Japan during summer and winter. Host tree species was the most significant factor affecting endophyte community composition.
Tubakia
species found at the study sites were divided into five specialists and three generalists according to their relative abundance in each host species and their host ranges. Specialists were dominant on their own host in summer, and their abundance declined in winter. To test the hypothesis that generalists are more widely adapted to their environment than specialists, we compared their spore germination rates at different temperatures. Spores of generalist
Tubakia
species were more tolerant of colder temperatures than were spores of specialist
Tubakia
species, supporting our hypothesis. Seasonal and site variations among
Tubakia
species were also consistent with our hypothesis. Host identity and ecology were significantly associated with endophyte community structure.
Toxigenic species belonging to Bacillus cereus sensu lato, including Bacillus thuringiensis, cause foodborne outbreaks thanks to their capacity to survive as spores and to grow in food matrixes. The ...goal of this work was to assess by means of a genome-wide transcriptional assay, in the food isolate B. thuringiensis UC10070, the gene expression behind the process of spore germination and consequent outgrowth in a vegetable-based food model. Scanning electron microscopy and Energy Dispersive X-ray microanalysis were applied to select the key steps of B. thuringiensis UC10070 cell cycle to be analyzed with DNA-microarrays. At only 40 min from heat activation, germination started rapidly and in less than two hours spores transformed in active growing cells. A total of 1646 genes were found to be differentially expressed and modulated during the entire B. cereus life cycle in the food model, with most of the significant genes belonging to transport, transcriptional regulation and protein synthesis, cell wall and motility and DNA repair groups. Gene expression studies revealed that toxin-coding genes nheC, cytK and hblC were found to be expressed in vegetative cells growing in the food model.
•We study Bacillus gene expression during life cycle in a vegetable food model.•A total of 1646 genes were differentially modulated in the four studied stages.•After only 40 min from heat inactivation, spores start to germinate.•Bacillus cereus UC10070 presented truncated 23S rRNA in spores, not detectable in vegetative cells.
Growth of indoor fungi on gypsum Segers, F.J.J.; Laarhoven, K.A.; Wösten, H.A.B. ...
Journal of applied microbiology,
August 2017, 2017-Aug, 2017-08-00, 20170801, Letnik:
123, Številka:
2
Journal Article
Recenzirano
Aims
To have a better understanding of fungal growth on gypsum building materials to prevent indoor fungal growth.
Methods and Results
Gypsum is acquired by mining or as a by‐product of flue‐gas ...desulphurization or treatment of phosphate ore for the production of fertilizer. Natural gypsum, flue‐gas gypsum and phosphogypsum therefore have different mineral compositions. Here, growth of fungi on these types of gypsum was assessed. Conidia of the indoor fungi Aspergillus niger, Cladosporium halotolerans and Penicillium rubens were inoculated and observed using microscopic techniques including low‐temperature scanning electron microscopy. Elemental analysis of gypsum was done using inductively coupled plasma atomic emission spectroscopy and segmented flow analysis. Moisture content of the gypsum was determined using a dynamic vapour sorption apparatus. Aspergillus niger, C. halotolerans and P. rubens hardly germinated on natural gypsum and flue‐gas gypsum. The latter two fungi did show germination, outgrowth, and conidiation on phosphogypsum, while A. niger hardly germinated on this substrate. Other experiments show that C. halotolerans and P. rubens can develop in pure water, but A. niger does not.
Conclusions
The observations show that the lack of germination of three indoor fungi is explained by the low amount of phosphor in natural, flue‐gas and laboratory‐grade gypsum. Additionally, C. halotolerans and P. rubens can develop in pure water, while conidia of A. niger do not show any germination, which is explained by the need for organic molecules of this species to induce germination.
Significance and Impact of the Study
Indoor fungal growth is a potential threat to human health and causes damage to building materials. This study possibly helps in the application of the right type of gypsum in buildings.
The hereditary disorders chorea acanthocytosis and Cohen syndrome are caused by mutations in different members of a family of genes that are orthologs of yeast VPS13. In vegetatively growing yeast, ...VPS13 is involved in the delivery of proteins to the vacuole. During sporulation, VPS13 is important for formation of the prospore membrane that encapsulates the daughter nuclei to give rise to spores. We report that VPS13 is required for multiple aspects of prospore membrane morphogenesis. VPS13 (1) promotes expansion of the prospore membrane through regulation of phosphatidylinositol phosphates, which in turn activate the phospholipase D, Spo14; (2) is required for a late step in cytokinesis that gives rise to spores; and (3) regulates a membrane-bending activity that generates intralumenal vesicles. These results demonstrate that Vps13 plays a broader role in membrane biology than previously known, which could have important implications for the functions of VPS13 orthologs in humans.
In this review, we examine the fungal spore killers. These are meiotic drive elements that cheat during sexual reproduction to increase their transmission into the next generation. Spore killing has ...been detected in a number of ascomycete genera, including
,
,
,
, and Fusarium. There have been major recent advances in spore killer research that have increased our understanding of the molecular identity, function, and evolutionary history of the known killers. The spore killers vary in the mechanism by which they kill and are divided into killer-target and poison-antidote drivers. In killer-target systems, the drive locus encodes an element that can be described as a killer, while the target is an allele found tightly linked to the drive locus but on the nondriving haplotype. The poison-antidote drive systems encode both a poison and an antidote element within the drive locus. The key to drive in this system is the restricted distribution of the antidote: only the spores that inherit the drive locus receive the antidote and are rescued from the toxicity of the poison. Spore killers also vary in their genome architecture and can consist of a single gene or multiple linked genes. Due to their ability to distort meiosis, spore killers gain a selective advantage at the gene level that allows them to increase in frequency in a population over time, even if they reduce host fitness, and they may have significant impact on genome architecture and macroevolutionary processes such as speciation.
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