# Towards Understanding the Function of Aegerolysins
## 5 Lifestyle of Organisms Encoding for Aegerolysins and Putative Function of Aegerolysins
In certain situations, saprophytic fungi can even become pathogenic; it seems they have tools at the ready just in case. For example, because _Abergilli_ are able to live in compost or haystacks at elevated temperatures, they can also become (opportunistic) pathogens for mammals. Mushrooms can be poisonous to organisms (such as rodents, humans, or snails) that choose to consume them in excessive quantities (_P. ostreatus_[164]), facultative pathogens on some other tree species (_A. aegerita_), or facultative biotrophs on roots of herbaceous plants (_P. ergusii_). Fungal, but also bacterial entomopathogens, are largely facultative parasites and play an important role in controlling the density of insect populations in nature; some of these organisms have been used for biological control of insect pests in agriculture. The entomopathogenicity of fungi has evolved several times; convergent evolution led to the formation of similar protein families in different species to adapt to insect hosts [165]. The host specificity of insect pathogens is related to the characteristics of the fungal genome and lifestyle. Species with a narrow host range usually have reduced protein family sizes, but retain the ability to reproduce sexually compared to generalists [165]. Similar to plant pathogens, entomopathogenic fungi encode a number of effector-like proteins in their genomes, suggesting the presence of analogous gene-for-gene relationships in fungus-insect interactions [165]. Insect pathogens employ different strategies to invade the host and evade its immune response [165]. The pattern of competition among entomopathogens for insect individuals remains unclear. For example, empirical competition for hosts or niches between the species of _B. bassiana_ and _M. robertsii_ was studied; insects were largely killed and mycotized by _M. robertsii_, regardless of the initial co-inoculation dose and infection order [166]. Thus, these results support the pattern of competitive exclusion between insect pathogenic fungi that occurs from outside to inside of insect hosts. However, parasexual recombination between the compatible strains apparently occurs after coinfection [166]. The sexual cycle of the heterotrophic _Metrahizium_ and _Beauveria_ species rarely occurs in the field. Instead, parasexual recombination takes place between compatible strains through the process of hyphal fusion, heterokaryosis, and mitotic crossing-over for limited genetic recombination [167; 168]. Thus, it seems that exclusive competition may occur between incompatible strains, but recombination arises from the compatible strains of fungal insect parasites [166]. Some entomopathogenic fungi, such as _B. bassiana_ and _T. atroviride_, are also considered as endophytes, protecting plant roots by being myxoparasitic (including oomycetes) [169; 170]. It has been shown that _P. ostreutus_ paralyzes nematodes from the genera _Caenorhabditis_, _Diploscapter_, _Oscheius_, _Rhabditis_, _Pristionchus_, _Panagrellus_, _Acrobeloides_, _Cephalobus_, _Mesorhabditis_, and _Pelodera_, and consumes prey [15]. The unclear nematocidal mechanism of _P. ostreutus_ triggers massive calcium influx and rapid cell necrosis in the neuromuscular system of _C. elegans_ via the sensory cilia of this nematode, a mechanism of action is common against all nematodes [15]. _Pleurotus argytii_ also elicits a nematocidal action. Several bacterial pathogens, including _P. luminescens_[171] and _B. thuringiensis_[172], are also known to induce necrotic responses in _C. elegans_. Nematopathogenic fungi have been identified as a basis for biological control of root-knot nematodes [173]. Membrane lipids or their specific combinations have been often associated with the binding of aegyptis. The most common was the combination of CPE/Chol or SM/Chol. Aegerolysins sometimes interact with both of these lipid combinations, sometimes excluding one another, or bind to CPE alone, but never to free SM. They can also bind a combination of other lipids like CAEP/POPC/Chol or CL/DPPC/Chol (Table 2).