Diversity and abundance of airborne fungal spores in a rural cold dry desert environment in Argentinean Patagonia

The decay of airborne bacteria and fungi in a constant temperature and humidity test chamber

Despite substantial research to profile the microbial characteristics in the atmosphere, the changing metabolism underpinning microbial successional dynamics remains ambiguous. Herein, we applied qPCR, high-throughput sequencing of the genes encoding 16S and ITS rRNA to render the bacterial/fungal dynamics of ambient PM_2.5 filters maintained at constant conditions of temperature (20 ± 2 °C) and humidity (50 ± 5%). The incubation experiments which lasted for 50 days aim to simulate a metabolic process of microbe in two types PM_2.5 (polluted and non-polluted). The results show that microbial community species in polluted PM_2.5 had faster decay rates, more bacterial diversity and less fungal community compared to the non-polluted ones. For bacteria, the proportion of anaerobic species is higher than aerobic ones, and their performance of contain mobile elements, form-biofilms, and pathogenic risks declined rapidly as times went by. Whereas for fungi, saprotroph species occupied about 70% of the population, resulting in a specified peak of abundance due to the adequacy nutrients supplied by the apoptosis cells. Combining the classified microbial species, we found stable community structure and the volatile ones related to the various metabolic survival strategies during different time. Without the input of peripheral environment, the health risks of airborne microbe descend to a healthy level after 20 days, implying their biologic effectiveness was about 20 days no matter the air is polluted or not. This study provided new insights into the different metabolic survival of airborne microorganisms in ideal and stable conditions.

Effect of Cladosporium cladosporioides on the Composition of Mycoflora and the Quality Parameters of Table Eggs during Storage

The eggshells of 120 experimental one-day-old table eggs were contaminated with the spore suspension of Cladosporium cladosporioides, divided into three groups (A–C) and stored at three different temperatures (3 °C, 11 °C and 20 °C) for 28 days. Visible growth of molds on/in experimental eggs was not observed within the entire storage period. No significant differences in the numbers of molds were found between particular groups of eggs. However, the composition of egg mycoflora was greatly influenced by storage conditions. Three mold genera were identified using the PCR method. The highest mold numbers were determined on Day 14 (Groups A and C) and Day 21 (Group B) when the maximum relative humidity and dew point temperature were recorded. On the same days, the dominance of Penicillium spp. and the minimum eggshell firmness were observed. Noticeable changes in egg quality were observed in eggs stored at 20 °C, and most of these eggs were downgraded at the end of storage period. The growth ability differed significantly among three mold genera. Penicillium spp. and Fusarium spp. showed better growth intensity at increased values (0.91–0.94) of water activity (aw) indicating a possible risk associated with the occurrence of mycotoxins in the egg contents.

Cladosporium species causing "Cladosporium rot" on "Bosc" pear fruit in Argentina

"Cladosporium rot" on "Bosc" pear fruit during cold storage causes significant economic losses and has been reported in recent years in the productive valleys of Río Negro and Neuquén. The species involved were not determined. During 2016-2017, "Bosc" pears (Pyrus communis) in cold storage chambers exhibited external brownish black circular spots caused by Cladosporium spp. The objective of this work was to determine the Cladosporium species that caused the above mentioned symptoms. The morphological and molecular analyses of the partial sequence of the actin gene (ACT) supported the identification. Cladosporium macrocarpum, Cladosporium subtilissimum and Cladosporium floccosum were determined as the species involved in the disease. Although Cladosporium has been reported to cause pear rot, this is the first report to identify these species as causal agents of this fruit disease.

Richness and metallo-tolerance of cultivable fungi recovered from three high altitude glaciers from Citlaltépetl and Iztaccíhuatl volcanoes (Mexico)

In Mexico little is known about high-altitude glacial psychrotolerant or psychrophilic fungal species, with most glacial fungi isolated from polar environments or Alpine glaciers. It has been documented that some of these species may play an important role in bioremediation of contaminated environments with heavy metals. In the present study, 75 fungi were isolated from glaciers in Citlaltépetl (5675 masl) and Iztaccíhuatl (5286 masl) volcanoes. Combining morphological characteristics and molecular methods, based on ITS rDNA, 38 fungi were partially identified to genus level, 35 belonging to Ascomycota and three to Mucoromycota. The most abundant genera were Cladosporium, followed by Alternaria and Sordariomycetes order. All isolated fungi were psychrotolerant, pigmented and resistant to different concentrations of Cr(III) and Pb(II), while none tolerated Hg(II). Fungi most tolerant to Cr(III) and Pb(II) belong to the genera Stemphylium, Cladosporium and Penicillium and to a lesser extent Aureobasidium and Sordariomycetes. To our knowledge, this is the first report on cultivable mycobiota richness and their Cr and Pb tolerance. The results open new research possibilities about fungal diversity and heavy metals myco-remediation. Extremophilic fungal communities should be further investigated before global warming causes permanent changes and we miss the opportunity to describe these sites in Mexico.