Actinomycetes from Caves: An Overview of Their Diversity, Biotechnological Properties, and Insights for Their Use in Soil Environments

Abstract

The environmental conditions of caves shape microbiota. Within caves’ microbial communities, actinomycetes are among the most abundant bacteria. Cave actinomycetes have gained increasing attention during the last decades due to novel bioactive compounds with antibacterial, antioxidant and anticancer activities. However, their potential role in soil environments is still unknown. This review summarises the literature dealing with actinomycetes from caves, underlining for the first time their potential roles in soil environments. We provide an overview of their diversity and biotechnological properties, underling their potential role in soil environments applications. The contribution of caves’ actinomycetes in soil fertility and bioremediation and crops biostimulation and biocontrol are discussed. The survey on the literature show that several actinomycetes genera are present in cave ecosystems, mainly Streptomyces, Micromonospora, and Nocardiopsis. Among caves’ actinomycetes, Streptomyces is the most studied genus due to its ubiquity, survival capabilities, and metabolic versatility. Despite actinomycetes’ outstanding capabilities and versatility, we still have inadequate information regarding cave actinomycetes distribution, population dynamics, biogeochemical processes, and metabolisms. Research on cave actinomycetes needs to be encouraged, especially concerning environmental soil applications to improve soil fertility and health and to antagonise phytopathogens.

Actinomycete Potential as Biocontrol Agent of Phytopathogenic Fungi: Mechanisms, Source, and Applications

“…Competition is an indirect mechanism of actinomycetes for the growth inhibition of phytopathogenic fungi [ 8 ]. Competence between two or more microorganisms begins for the same carbon source (carbohydrates such as sucrose, glucose, maltose, and fructose) or space for their growth [ 32 , 33 ]. The ecological plasticity and fast growth of antagonistic microorganisms allow them to assimilate the available nutrients in the host at a greater amount than phytopathogenic fungi; thus, the spore germination stage and infection processes to the host are reduced [ 34 ].…”

“…Actinomycetes have been isolated from different hypersaline environments, such as salt lakes, salt flats, salt mines, and brine wells; however, these environments remain unexplored [ 6 ]. Compounds and secondary metabolites of terrestrial microorganisms have been studied extensively, hence the importance of searching for new isolation sources for actinomycetes [ 33 ].…”

“…The success of a biocontrol agent is its formulation, which must include a specific concentration of the new microorganisms and a set of other inert ingredients to produce a commercial product for its use in field conditions, and must show repeated positive results, reasonable prices and easy handling [ 17 ]. The efficiency of these biocontrol agents is affected by environmental factors, such as temperature, humidity, precipitation, among other abiotic aspects which synthetic fungicides have overcome [ 33 ].…”

On the Selective Isolation of Actinobacteria from Different Mexican Ecosystems

“…Soil is one of the most complex, dynamic, and in constant evolution ecosystem and so it surely is its actinobacteria portion. Soil actinobacteria, particularly Streptomyces is still a never-ending source for the discovery of secondary metabolites with diverse biological activities [13,14,26] and due to its ubiquity, survival capabilities, and metabolic versatility, it is the most studied genus within the class Actinobacteria [2,15]. The diversity of actinobacteria isolated from SI at RANP shows the potential of our study [40] and represents the entree to explore its secondary or specialized metabolite potential [13-16, 41, 42] and diversity.…”

“…Microorganisms and microbial biomass, including actinobacteria, represent the major resource for biotechnology and biological areas. We should continue exploring their role in nature in order to understand their biology, ecology, and bioprospecting potential [13][14][15][16].…”