Bacillus cytotoxicus Isolated from a Pristine Natural Geothermal Area Reveals High Keratinolytic Activity

Abstract

Geothermal areas are the niches of a rich microbial diversity that is not only part of the intangible patrimony of a country but also the source of many microbial species with potential biotechnological applications. Particularly, microbial species in geothermal areas in Argentina have been scarcely explored regarding their possible biotechnological uses. The purpose of this work was to explore the proteolytic and keratinolytic enzymatic potential of microorganisms that inhabit in the Domuyo geothermal area in the Neuquén Province. To this end, we did enrichment cultures from two high-temperature natural samples in mineral media only supplemented with whole chicken feathers. After the isolation and the phylogenetic and morphologic characterization of different colonies, we obtained a collection of Bacillus cytotoxicus isolates, a species with no previous report of keratinolytic activity and only reported in rehydrated meals connected with food poisoning outbreaks. Its natural habitat has been unknown up to now. We characterized the proteolytic and keratinolytic capacities of the B. cytotoxicus isolates in different conditions, which proved to be remarkably high compared with those of other similar species. Thus, our work represents the first report of the isolation as well as the keratinolytic capacity characterization of strains of B. cytotixicus obtained from a natural environment.

Further Insights into the Toxicity of Bacillus cytotoxicus Based on Toxin Gene Profiling and Vero Cell Cytotoxicity Assays

“…The ecological niche of B. cytotoxicus and the contamination pathway of potato products, however, remain unclear. Indeed, the first isolation of this species from a natural habitat (geothermal areas) was published only recently, but it does not provide any indication of potential food contamination pathways [ 15 ]. Stevens, et al [ 4 ] revealed that B. cytotoxicus harbors a putative hydroxyphenylalanine ( hpa ) operon, which is absent in the genomes of other B. cereus group members.…”

The Food Poisoning Toxins of Bacillus cereus

“…The authors concluded that this putative evolutionary advantage might have been the reason for species differentiation [ 410 ]. Recently, Cavello et al first reported the isolation of B. cytotoxicus from the natural environment, a geothermal area, as well as its keratinolytic activity [ 411 ]. Interestingly, cytK-2 is not present in B. anthracis [ 125 ], but has been found in B. mycoides [ 412 ], very frequently in B. thuringiensis [ 125 , 210 ], and also outside the B. cereus group in Paenibacillus cookie [ 413 ].…”

Structure, Application, and Biochemistry of Microbial Keratinases

“…Although many keratinase producers have been isolated and identified ( Cavello et al, 2020 ; Jagadeesan et al, 2020 ; Moridshahi et al, 2020 ; Nnolim et al, 2020b ; Reis et al, 2020 ), the isolation and characterization of keratinase-producing microorganisms are still an important task. The keratin degradation efficiency can be improved when more keratinases are applied ( Peng et al, 2019 ).…”