Neocallimastix was the first anaerobic fungal genus to be characterized, challenging the dogma of the time that all fungi respired. It was the ground-breaking work of Professor Colin Orpin that led to the true identity of anaerobic fungi being documented and accepted in the scientific community.
Prior to this, the organism was identified as a flagellated protozoan that was named Callimastix frontalis by Braune (1913), and was later renamed by Vavra & Joyon (1966) to Neocallimastix frontalis.
To date, several different Neocallimastix species have been mentioned in the scientific literature, although not all have been validly characterized and may not be distinct. Neocallimastix frontalis is the type species, with the formal description of this species actually dating back to Callimastix frontalis in 1913 according to Heath et al (1983). There is no current consensus as to the type strain, as different isolates were characterized in the early work with no single type strain clearly specified.
Within the family Neocallimastigaceae, Neocallimastix is phylogenetically most closely related to Aestipascuomyces, Feramyces, Orpinomyces, Pecoramyces and Ghazallamyces (when using LSU as a taxonomic marker).
Images are shown above of a recently isolated Neocallimastix frontalis culture, strain Hef5.
N. frontalis produces beige circular colonies with a dark center of sporangial structure (Image 1). It exhibits thin biofilm-like growth in liquid medium (Image 2).
Neocallimastix produces polyflagellated zoospores (with 7-30 flagella per zoospore) (Images 3 & 4).
Neocallimastix has a monocentric thalli with both endogenous (Image 5) and exogenous (Images 6 & 7) sporangia.
For Neocallimastix frontalis strain Hef5 that is pictured above, the LSU sequence is available in the NCBI database (accession number MG992494).