A High Diversity in Chitinolytic and Chitosanolytic Species and Enzymes and Their Oligomeric Products Exist in Soil with a History of Chitin and Chitosan Exposure

Abstract

Chitin is one of the most abundant biomolecules on earth, and its partially de-N-acetylated counterpart, chitosan, is one of the most promising biotechnological resources due to its diversity in structure and function. Recently, chitin and chitosan modifying enzymes (CCMEs) have gained increasing interest as tools to engineer chitosans with specific functions and reliable performance in biotechnological and biomedical applications. In a search for novel CCME, we isolated chitinolytic and chitosanolytic microorganisms from soils with more than ten-years history of chitin and chitosan exposure and screened them for chitinase and chitosanase isoenzymes as well as for their patterns of oligomeric products by incubating their secretomes with chitosan polymers. Of the 60 bacterial strains isolated, only eight were chitinolytic and/or chitosanolytic, while 20 out of 25 fungal isolates were chitinolytic and/or chitosanolytic. The bacterial isolates produced rather similar patterns of chitinolytic and chitosanolytic enzymes, while the fungal isolates produced a much broader range of different isoenzymes. Furthermore, diverse mixtures of oligosaccharides were formed when chitosan polymers were incubated with the secretomes of select fungal species. Our study indicates that soils with a history of chitin and chitosan exposure are a good source of novel CCME for chitosan bioengineering.

Chitin and chitin-related compounds in plant–fungal interactions

“…Moreover, during chitin amendment, microbial communities shifted in both the abundances and structures of both of total soil bacteria actinobacteria, Oxalobacteriaceae and fungi, in particular, Verticillium dahliae were recorded (Cretoiu et al 2013). The richness of family-18 glycosyl hydrolase chitinase genes carried by the soil bacteria was also revealed in chitin- (Cretoiu et al 2013) and chitosan-treated soil (Nampally et al 2015). Chitin amendment in soil increases the vegetative growth of plants.…”

Resolving the Mortierellaceae phylogeny through synthesis of multi-gene phylogenetics and phylogenomics

“…Fresh isolates for this study were also obtained from roots, soils and plant substrates collected across Australia, Fiji, New Zealand, Uganda, and the United States (Supplementary Table 2). Isolates were obtained using three methods: soil baiting, shrimp baiting, and soil dilution plating or swabbing (Benny 2008;Finkelstein 2013;Nampally et al 2015). Soil baiting involved placing substrates in squares of water agar (10 g/L Bacto-Agar (Difco)) supplemented with antibiotics (i.e.…”

“…Aerial hyphae able to colonize the upper plate were then transferred to new 1% malt extract agar (MEA: 10 g/L Malt extract, 1 g/L Yeast extract, and 10 g/L Bac-toAgar (Difco)) plates. Shrimp baiting refers to incubating soils with shrimp exoskeletons, which have been washed and sterilized (Shirouzu et al 2012;Nampally et al 2015). This substrate is enriched in chitin and selects for chitinolytic fungi, which includes many Mortierella species (Shirouzu et al 2012;Nampally et al 2015).…”

Arbuscular mycorrhiza and soil organic nitrogen: network of players and interactions

“…Further examples of experimentally measured N transfer rates from organic N sources to plants via AMF hyphae are provided in Table 1. Such efficient release and transport of N as quoted above would require very fast chitin mineralization, for example, by specialized soil prokaryotes and/or fungi [12,94] and further processing via the soil microbial loop involving microbial grazers [15]. It is noteworthy that chitinolytic microorganisms usually degrade chitin to oligomers that are directly taken to their cells via specialized transporters, referred to (at least in the prokaryotic world) as chitoporins ( [12] and references therein).…”