Aspergillus wentii

''Aspergillus wentii'' is an asexual, filamentous, endosymbiotic fungus belonging to the mold genus, ''Aspergillus''. It is a common soil fungus with a cosmopolitan distribution, although it is primarily found in subtropical regions. Found on a variety of organic materials, ''A. wentii'' is known to colonize corn, cereals, moist grains, peanuts and other ground nut crops. It is also used in the manufacture of biodiesel from lipids and is known for its ability to produce enzymes used in the food industry.

History and taxonomy

''Aspergillus wentii'' was first described by German mycologist Carl Friedrich Wilhelm Wehmer in 1896. Following a morphology-based classification scheme he created in 1901, Wehmer grouped ''A. wentii'' under a category of large ''Aspergilli'' that he called the "Macroaspergilli" due to its large fruiting body structure (the conidial head). The taxonomic position of ''A. wentii'' remained unclear within the genus as ''A. wentii'' Wehmer synonyms (''A. archaeoflavus'' Blochwitz and ''Aspergillus wentii'' var. ''minimus'') were presented by Drs. Charles Thom and Kenneth Raper as possible variations or strains. The first ''A. wentii'' group was proposed by Drs. Thom and Raper in 1945. This original ''A. wentii'' group was classified under the Circumdati subgenus of the genus ''Aspergillus'' and included 4 fungal species currently known as '' A. avenaceus'' Smith, '' A. panamensis'' Raper and Thom, ''A. alliaceus'' Thom and Church, and ''A. wentii'' Wehmer. Presently, ''Aspergillus wentii'' Wehmer is the only remaining fungus of the four fungi that originally made up the "''A. wentii'' group". The 3 former members of the ''A. wentii'' group (''A. avenaceus'', ''A. panamensis'', and ''A. alliaceus'') have since been reassigned to different ''Aspergillus'' subgenera (''A. flavus'' group, ''A. ustus'' group, and ''A. ocheaceus'' group) respectively. Drs. Charles Thom and Dorothy Fennell revised the ''A. wentii'' group in 1965 to include ''Aspergillus thomii'' Smith and ''A. terricola'' Marchal along with ''A. wentii'' Wehmer. However, ''Aspergillus'' group classifications within subgenera became obsolete in the 1980s being replaced by sections.

The new ''Aspergilli'' sections adapted and revised previously established morphological and physiological characteristics of ''Aspergillli'' groups and incorporated DNA sequencing analyses to confirm phylogenetic relationships among related ''Aspergilli''. Many species were reassigned to new ''Aspergilli'' sections as phylogenetic relationships were confirmed by DNA and genome sequencing experiments. As a result, ''A. wentii'' and '' A. dimorphicus'', previously described as synonyms within the ''A. wentii'' section, were later confirmed to be distinct species.

Growth and morphology

''Aspergillus wentii'' produces single-celled, globose, conidia (singular conidium) in unbranched, filamentous chains. Young asexual conidia (also called spores) start off smooth, colourless, and ellipsoidal before maturing into rough, globose spores approximately 4.5–5 µm in diameter. ''Aspergillus wentii'' conidia can appear anywhere from darker yellow to brown in colour when mature and have a single wall, unlike related species ''Aspergillus tamarii'' whose conidia have a double wall membrane. The elongating chains of conidia are dispersed through slightly pigmented, vase-shaped structures known as phialides that are around 6–8 µm. The phialides sit on top of almond-shaped structures known as metulae that are about 10–20 µm in length and also slightly pigmented. Together, these metulae and phialides structures radiate outward from a spheroid structure known as the vesicle, layering around its entire surface area. The vesicle can grow to a diameter of 80 µm, with a completely fertile spheroid surface area. Collectively, this large globose complex made up of the vesicle at the centre with metulae and phialides radiating outward is called the conidial head. The conidial head can vary from tan-yellow to darker coffee-coloured brown and grow as big as 500–800 µm in diameter. The conidial head is affixed atop of a thick, aseptate stalk known as a stipe. ''Aspergillus wentii'' stipes are notable for being interspersed and longer than average ''Aspergillus'' stalks. The stipe and conidial head together form a translucent, rod-shaped structure collectively known as the conidiophore that in turn, extends from the hyphal tip. The conidiophore can grow anywhere between 3–5 millimeters in length, has a glassy appearance (described as hyaline) and typically have a smooth texture, although granular conidiophores have been observed. ''Aspergillus wentii'' produces aerial hyphae, white or sometimes yellow in colour that can grow to a few millimeters in length. ''Aspergillus wentii'' foot cells have dense walls and are branched.

Overall, ''Aspergillus wentii'' colonies appear dense, floccose