Mitonuclear Genetic Interactions in the Basidiomycete Heterobasidion parviporum Involve a Non-conserved Mitochondrial Open Reading Frame

The mitochondrial and nuclear genomes of Eukaryotes are inherited separately and consequently follow distinct evolutionary paths. Nevertheless, the encoding of many mitochondrial proteins by the nuclear genome shows the high level of integration they have reached, which makes mitonuclear genetic interactions all the more conceivable. For each species, natural selection has fostered the evolution of coadapted alleles in both genomes, but a population-wise divergence of such alleles could lead to important phenotypic variation, and, ultimately, to speciation. In this study in the Basidiomycete Heterobasidion parviporum, we have investigated the genetic basis of phenotypic variation among laboratory-designed heterokaryons carrying the same pair of haploid nuclei, but a different mitochondrial genome. Radial growth rate data of thirteen unrelated homokaryotic parents and of their heterokaryotic offspring were combined with SNP data extracted from parental genome sequences to identify nuclear and mitochondrial loci involved in mitonuclear interactions. Two nuclear loci encoding mitochondrial proteins appeared as best candidates to engage in a genetic interaction affecting radial growth rate with a non-conserved mitochondrial open reading frame of unknown function and not reported apart from the Russulales order of Basidiomycete fungi. We believe our approach could be useful to investigate several important traits of fungal biology where mitonuclear interactions play a role, including virulence of fungal pathogens.

Biofilm Growth Under Elastic Confinement

Bacteria often form surface-bound communities, embedded in a self-produced extracellular matrix, called biofilms. Quantitative studies of their growth have typically focused on unconfined expansion above solid or semi-solid surfaces, leading to exponential radial growth. This geometry does not accurately reflect the natural or biomedical contexts in which biofilms grow in confined spaces. Here we consider one of the simplest confined geometries: a biofilm growing laterally in the space between a solid surface and an overlying elastic sheet. A poroelastic framework is utilised to derive the radial growth rate of the biofilm; it reveals an additional self-similar expansion regime, governed by the stiffness of the matrix, leading to a finite maximum radius, consistent with our experimental observations of growing Bacillus subtilis biofilms confined by PDMS.

Comparative study of fungal stability between Metarhizium strains after successive subculture

Background Metarhizium species are considered one of the most outstanding powerful biological control agents that have been commercialized as biopesticides against various agricultural pests. Fungal stability with successive in vitro cultivation is a desirable trait for a large-scale production of fungal biopesticide. Main body The new Egyptian strain Metarhizium anisopliae AUMC 3262 exhibited auspicious results when compared to Metarhizium brunneum ARSEF 4556 and M. brunneum V275 based on the variations of fungal characteristics, and essential quality control parameters (radial growth rate, conidial yield, viability, and virulence) after repeated in vitro subculturing. Changes in morphological characteristics were noted at both AUMC 3262 and ARSEF 4556. Following the 5th subculture, decreased conidial yield was noted, though radial growth remained stable, confirming that there is a non-positive correlation between conidial yield and radial growth rate for these species. In contrast, V275 showed a high morphological stability, conidial yield, and radial growth rate after repeated subculture. The three tested strains manifested high viability up to 100% and displayed the same pattern of Pr1 production. A slight variation was recorded in the median lethal time (LT50) values against the great wax moth, Galleria mellonella (L.), larvae between different subcultures of the tested Metarhizium strains. Conclusion The new Egyptian strain AUMC 3262 showed a high stability with a slight difference in some parameters after the successive subculture compared to both ARSEF4556 and V275.

STABILITY OF THE STRAINS OF BASIDIOMYCETES DURING STORAGE IN THE COLLECTION

Basidial macromycetes may be a material for the development of new biotechnologies, medical preparations, components of dietary nutrition. Therefore, it is necessary for the highest level of quality for maintenance and identification of mushroom strains in the collection. An important parameter, in this case, is a stability of isolated and described collection strains of basidiomycetes. Stability is one of the key issues of long-term preservation of pure culture collections. For the collection of medicinal basidiomycetes of ONU I.I. Mechnikov, which preserves by the method of periodic reseeding of colonies the strain stability had not been studied yet. The goal of this research is to study the stability of this collection by a growth rate of mushroom colonies and electrophoretic spectra of carboxylesterases after different times of storage of cultures on malt agar. In this research the strains of three age categories (1, 2 and 3 years) of storage on malt-agar medium at temperature 4 ° С for were tested. The radial growth rate of their vegetative mycelium and the spectra of multiple molecular forms of carboxylesterases by the method of vertical electrophoresis in 7% of polyacrylamide gel were investigated. It was established that the stability of the radial growth rate of A. auricula-judae, F. velutipes, G. lucidum the vegetative mycelium after different storage periods is high according to the values of variation coefficients. At the same time, the expression of molecular forms of carboxylesterase showed sufficient variability. Partially conservative molecular forms were detected in some age groups of strains, as well as for individual strains. Thus the growth rate of colonies is a stable indicator and the molecular forms of carboxylesterases of different ages strains are variable.