Chitinases from Serratia marcescens Nima

Sequence analysis and docking performance of extracellular chitinase from Bacillus pumilus MCB-7, a novel mangrove isolate

Bacterial chitinases has a major role in chitinaceous waste management, biological control of pests and phytopathogens. In the present study, exochitinase gene ChitA encoding extracellular chitinase from the mangrove bacteria Bacillus pumilus MCB-07 was genetically characterized. Oligonucleotide primers specific to chitinase gene of Bacillus pumilus were designed and amplified by PCR. The purified PCR product was successfully cloned in pGEM-T vector and transformed into Escherichia coli DH5-α competent cells. Nucleotide sequence alignment of the chitinase gene revealed 96 % similarity whereas 94 % of the catalytic domain of 598 amino acids is conserved with protein family GH18 chitinases, which is a novel report for Bacillus pumilus. The insert also showed a number of substitutions (mutations) with other sp. of Bacillus which demonstrated that chitinase of Bacillus pumilus MCB-07 is a novel gene. Multiple sequence alignment of chitinase gene sequences and its predicted amino acid sequences were also evaluated and the sequence was deposited in GenBank with accession number KT966736.1. Homology modeling of the chitinase depicted the typical (α/β) 8 TIM barrel structure. Molecular docking of the protein was performed by Autodock 4.2.6 and the docked pocket contained Val 113, Met 114, Gln 99, Ala 75 and Cys 98 as the key binding residues. The molecular docking of Bacillus pumilus chitinase, revealed the involvement of a phenylalanine of the catalytic domain in the catalytic process of chitin to mono and oligomers of NAG. The amino acid exhibited both hydrophobic and hydrogen bond interactions of chitin molecules with phenylalanine.

Production and Potential Applications of Bioconversion of Chitin and Protein-Containing Fishery Byproducts into Prodigiosin: A Review

The technology of microbial conversion provides a potential way to exploit compounds of biotechnological potential. The red pigment prodigiosin (PG) and other PG-like pigments from bacteria, majorly from Serratia marcescens, have been reported as bioactive secondary metabolites that can be used in the broad fields of agriculture, fine chemicals, and pharmacy. Increasing PG productivity by investigating the culture conditions especially the inexpensive carbon and nitrogen (C/N) sources has become an important factor for large-scale production. Investigations into the bioactivities and applications of PG and its related compounds have also been given increased attention. To save production cost, chitin and protein-containing fishery byproducts have recently been investigated as the sole C/N source for the production of PG and chitinolytic/proteolytic enzymes. This strategy provides an environmentally-friendly selection using inexpensive C/N sources to produce a high yield of PG together with chitinolytic and proteolytic enzymes by S. marcescens. The review article will provide effective references for production, bioactivity, and application of S. marcescens PG in various fields such as biocontrol agents and potential pharmaceutical drugs.

Honeydew-associated microbes elicit defense responses against brown planthopper in rice

Feeding of sucking insects, such as the rice brown planthopper (Nilaparvata lugens; BPH), causes only limited mechanical damage on plants that is otherwise essential for injury-triggered defense responses against herbivores. In pursuit of complementary BPH elicitors perceived by plants, we examined the potential effects of BPH honeydew secretions on the BPH monocot host, rice (Oryza sativa). We found that BPH honeydew strongly elicits direct and putative indirect defenses in rice, namely accumulation of phytoalexins in the leaves, and release of volatile organic compounds from the leaves that serve to attract natural enemies of herbivores, respectively. We then examined the elicitor active components in the honeydew and found that bacteria in the secretions are responsible for the activation of plant defense. Corroborating the importance of honeydew-associated microbiota for induced plant resistance, BPHs partially devoid of their microbiota via prolonged antibiotics ingestion induced significantly less defense in rice relative to antibiotic-free insects applied to similar groups of plants. Our data suggest that rice plants may additionally perceive herbivores via their honeydew-associated microbes, allowing them to discriminate between incompatible herbivores-that do not produce honeydew-and those that are compatible and therefore dangerous.

Antifungal performance of extracellular chitinases and culture supernatants of Streptomyces galilaeus CFFSUR-B12 against Mycosphaerella fijiensis Morelet

The tropical and mycoparasite strain Streptomyces galilaeus CFFSUR-B12 was evaluated as an antagonist of Mycosphaerella fijiensis Morelet, causal agent of the Black Sigatoka Disease (BSD) of banana. On zymograms of CFFSUR-B12 culture supernatants, we detected four chitinases of approximately 32 kDa (Chi32), 20 kDa (Chi20), and two with masses well over 170 kDa (ChiU) that showed little migration during denaturing electrophoresis at different concentrations of polyacrylamide. The thymol-sulphuric acid assay showed that the ChiU were glycosylated chitinases. Moreover, matrix assisted laser desorption ionization time-of-flight MS analysis revealed that the ChiU are the same protein and identical to a family 18 chitinase from Streptomyces sp. S4 (gi|498328075). Chi32 was similar to an extracellular protein from Streptomyces albus J1074 (gi|478687481) and Chi20 was non-significantly similar to chitinases from five different strains of Streptomyces (P > 0.05). Subsequently, Chi32 and Chi20 were partially purified by anion exchange and hydrophobic interaction chromatography and tested against M. fijiensis. Chitinases failed to inhibit ascospore germination, but inhibited up to 35 and 62% of germ tube elongation and mycelial growth, respectively. We found that crude culture supernatant and living cells of S. galilaeus CFFSUR-B12 were the most effective in inhibiting M. fijiensis and are potential biocontrol agents of BSD.

Biotechnological approaches to develop bacterial chitinases as a bioshield against fungal diseases of plants

Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. An alternative approach to avoid the undesired effects of chemical control could be biological control using antifungal bacteria that exhibit a direct action against fungal pathogens. Several biocontrol agents, with specific fungal targets, have been registered and released in the commercial market with different fungal pathogens as targets. However, these have not yet achieved their full commercial potential due to the inherent limitations in the use of living organisms, such as relatively short shelf life of the products and inconsistent performance in the field. Different mechanisms of action have been identified in microbial biocontrol of fungal plant diseases including competition for space or nutrients, production of antifungal metabolites, and secretion of hydrolytic enzymes such as chitinases and glucanases. This review focuses on the bacterial chitinases that hydrolyze the chitinous fungal cell wall, which is the most important targeted structural component of fungal pathogens. The application of the hydrolytic enzyme preparations, devoid of live bacteria, could be more efficacious in fungal control strategies. This approach, however, is still in its infancy, due to prohibitive production costs. Here, we critically examine available sources of bacterial chitinases and the approaches to improve enzymatic properties using biotechnological tools. We project that the combination of microbial and recombinant DNA technologies will yield more effective environment-friendly products of bacterial chitinases to control fungal diseases of crops.

Generation of antibacterial oligosaccharides derived from chitin using heterologous endochitinase synthesized in Escherichia coli

AIMS

To synthesize two heterologous endochitinases in Escherichia coli and demonstrate their potential for applied use in generating antibacterial chitin-derived oligosaccharides (OGS).

METHODS AND RESULTS

Heterologous endochitinase genes, chiA Nima and chiA74, were expressed in E. coli. Endochitinases were secreted by the E. coli export machinery and by approximately 20 h maximal chitinolytic activity was observed. The highest chitinolytic activity was observed with ChiA Nima, which produced antibacterial OGS with activities against Enterobacter cloacae, Escherichia coli, Staphylococcus aureus and S. xylosus.

CONCLUSIONS

It was shown that the export machinery of E. coli is well suited for the secretion of bioactive ChiA74 and ChiA Nima endochitinases, and that the latter can generate antibacterial OGS.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study suggests that it is feasible to synthesize endochitinases ChiA Nima and ChiA74 codified by E. coli and mass-produce these enzymes in culture supernatants. As signal peptides in native ChiA Nima and ChiA74 were recognized by the protein export molecular apparatus in E. coli, these short peptides could be included as signal sequences for transport in E. coli of other proteins with applied value. This is the first report suggesting that ChiA Nima can be used to produce OGS to control food-borne pathogenic bacteria.

Expression of chitinase A (chiA) gene from a local isolate of Serratia marcescens in Coleoptera-specific Bacillus thuringiensis

AIMS

The present study focused on cloning and expression of chiA gene from a highly chitinolytic local isolate of Serratia marcescens in an anti-Coleopteran Bacillus thuringiensis and comparison of the characteristics of the native and recombinant ChiAs.

METHODS AND RESULTS

chiA gene from Ser. marcescens was cloned, sequenced and compared with the previously cloned chiA genes. chiA gene was PCR cloned and expressed in anti-Coleopteran B. thuringiensis strain 3023 as verified by Western blot analysis. Specific ChiA activity of the recombinant B. thuringiensis (strain 3023-SCHI) reached its highest level at 21st hour of growth (16.93 U mg(-1)), which was 5.2- and 1.3-fold higher than that of its parental strain and Ser. marcescens, respectively. Temperature and pH effects on native and recombinant ChiAs were next determined. The recombinant plasmid was quite stable over 240 generations.

CONCLUSIONS

Serratia marcescens ChiA was heterologously expressed in an anti-Coleopteran B. thuringiensis at levels even higher than that produced by the source organism.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bacillus thuringiensis 3023-SCHI co-expressing anti-Coleopteran Cry3Aa protein and Ser. marcescens chitinase offers a viable alternative to the use of chitinolytic microbes/enzymes in combination with entamopathogenic bacteria for an increased potency because of synergistic interaction between them.

Identification of a novel endochitinase from a marine bacterium Vibrio proteolyticus strain No. 442

Chitin binding proteins prepared from Vibrio proteolyticus were purified and the N-terminal amino-acid sequence of a protein from a 110-kDa band on SDS-PAGE was found to be 85-90% identical to the 22nd-41st residues of the N-termini of chitinase A precursor proteins from other vibrios. We cloned the corresponding gene, which encodes a putative protein of 850 amino acids containing a 26-residue signal sequence. The chitinase precursor from V. proteolyticus was 78-80% identical to those from Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio carchariae. However, the proteolytic cleavage site for C-terminal processing between R597 and K598 in the chitinase precursor of other vibrios was not observed in the amino acid sequence of V. proteolyticus, which instead had the sequence R600 and A601. Subsequently, full-length and truncated chitinases were generated in Escherichia coli. The specific activity of full-length chitinase expressed in E. coli was 17- and 20-folds higher for colloidal and alpha-chitins (insoluble substrate), respectively, than that of the C-terminal truncated enzyme. However, both recombinants showed similar hydrolysis patterns of hexa-N-acetyl-chitohexaose (soluble substrate), producing di-N-acetyl-chitobiose as major product on TLC analysis. We showed that the C-terminus of the V. proteolyticus chitinase A was important for expression of high specific activity against insoluble chitins.

Human gastric juice contains chitinase that can degrade chitin

Chitin digestion by humans has generally been questioned or denied. Only recently chitinases have been found in several human tissues and their role has been associated with defense against parasite infections and to some allergic conditions. In this pilot study we tested the gastric juices of 25 Italian subjects on the artificial substrates 4-methylumbelliferyl-beta-D-N,N',diacetylchitobiose or/and fluorescein isothiocyanate (FITC) chitin to demonstrate the presence of a chitinase activity. Since this chitinase activity was demonstrated at acidic pH, it is currently referred to acidic mammalian chitinase (AMCase). AMCase activity was present in gastric juices of twenty of 25 Italian patients in a range of activity from 0.21 to 36.27 nmol/ml/h and from 8,881 to 1,254,782 fluorescence emission (CPS), according to the used methods. In the remaining five of 25 gastric juices, AMCase activity was almost absent in both assay methods. An allosamidine inhibition test and the measurement at different pH values confirmed that this activity was characteristic of AMCase. The absence of activity in 20% of the gastric juices may be a consequence of virtual absence of chitinous food in the Western diet.

Bacterial chitinases: properties and potential

Chitin is among the most abundant biomass present on Earth. Chitinase plays an important role in the decomposition of chitin and potentially in the utilization of chitin as a renewable resource. During the previous decade, chitinases have received increased attention because of their wide range of applications. Chito-oligomers produced by enzymatic hydrolysis of chitin have been of interest in recent years due to their broad applications in medical, agricultural, and industrial applications, including antibacterial, antifungal, hypocholesterolemic, and antihypertensive activity, and as a food quality enhancer. Microorganisms, particularly bacteria, form one of the major sources of chitinase. In this article, we have reviewed some of the chitinases produced by bacterial systems that have gained worldwide research interest for their diverse properties and potential industrial uses.