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Diversity of thermophilic and thermotolerant fungi in corn grain.

ABSTRACT: Corn bins in the midwestern United States can reach temperatures up to 52 C. High temperatures combined with sufficient moisture and humidity in bins provide the perfect environment to promote the growth of thermophilic and thermotolerant fungi. In this article, we characterize for the first time thermophilic and thermotolerant fungi in corn grain bins using culture-based methods and pyrosequencing techniques. Corn samples were collected from local farms in western Illinois. Samples were plated and incubated at 50 C using a variety of approaches. Of several hundred kernels examined, more than 90% showed colonization. Species identified using culture methods included Thermomyces lanuginosus, Thermomyces dupontii, Aspergillus fumigatus, Thermoascus crustaceus, and Rhizomucor pusillus. Pyrosequencing was also performed directly on corn grain using fungal-specific primers to determine whether thermophilic fungi could be detected using this technique. Sequences were dominated by pathogenic fungi, and thermophiles were represented by less than 2% of the sequences despite being isolated from 90% of the grain samples using culturing techniques. The high abundance of previously undocumented viable fungi in corn could have negative implications for grain quality and pose a potential risk for workers and consumers of corn-derived products in the food industry. Members of the Sordariales were absent among thermophile isolates and were not represented in nuc rDNA internal transcribed spacer (ITS) sequences. This is in striking contrast with results obtained with other substrates such as litter, dung, and soils, where mesophilic and thermophilic members of the Sordariaceae and Chaetomiaceae are common. This absence appears to reflect an important difference between the ecology of Sordariales and other orders within the Ascomycota in terms of their ability to compete in microhabitats rich in sugars and living tissues.

SUBMITTER: Sandona K

PROVIDER: S-EPMC6801065 | biostudies-literature | 2019 Sep-Oct

REPOSITORIES: biostudies-literature

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Diversity of thermophilic and thermotolerant fungi in corn grain.

Sandona Katrina K Billingsley Tobias Terri L TL Hutchinson Miriam I MI Natvig Donald O DO Porras-Alfaro Andrea A

Mycologia 20190726 5

Corn bins in the midwestern United States can reach temperatures up to 52 C. High temperatures combined with sufficient moisture and humidity in bins provide the perfect environment to promote the growth of thermophilic and thermotolerant fungi. In this article, we characterize for the first time thermophilic and thermotolerant fungi in corn grain bins using culture-based methods and pyrosequencing techniques. Corn samples were collected from local farms in western Illinois. Samples were plated ...[more]

PMID: 31348716

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Project description:Composting is a complex process in which various micro-organisms, mainly fungi and bacteria, are involved. The process depends on a large number of factors (biological, chemical, and physical) among which microbial populations play a fundamental role. The high temperatures that occur during the composting process indicate the presence of thermotolerant and thermophilic micro-organisms that are key for the optimization of the process. However, the same micro-organisms can be harmful (allergenic, pathogenic) for workers that handle large quantities of material in the plant, and for end users, for example, in the indoor environment (e.g., pots in houses and offices). Accurate knowledge of thermotolerant and thermophilic organisms present during the composting stages is required to find key organisms to improve the process and estimate potential health risks. The objective of the present work was to study thermotolerant and thermophilic mycobiota at different time points of compost maturation. Fungi were isolated at four temperatures (25, 37, 45, and 50 °C) from compost samples collected at five different steps during a 21-day compost-maturation period in an active composting plant in Liguria (northwestern Italy). The samples were subsequently plated on three different media. Our results showed a high presence of fungi with an order of magnitude ranging from 1 × 104 to 3 × 105 colony-forming units (CFU) g-1. The isolated strains, identified by means of specific molecular tools (ITS, beta-tubulin, calmodulin, elongation factor 1-alpha, and LSU sequencing), belonged to 45 different species. Several thermophilic species belonging to genera Thermoascus and Thermomyces were detected, which could be key during composting. Moreover, the presence of several potentially harmful fungal species, such as Aspergillus fumigatus, A. terreus, and Scedosporium apiospermum, were found during the whole process, including the final product. Results highlighted the importance of surveying the mycobiota involved in the composting process in order to: (i) find solutions to improve efficiency and (ii) reduce health risks.

Dataset Information

Diversity of thermophilic and thermotolerant fungi in corn grain.

Publications

Diversity of thermophilic and thermotolerant fungi in corn grain.

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