Development of a method for the detection and quantification of total chitinase activity by digital analysis

A set of simple methods for detection and extraction of laminarinase

A carefully designed ammonium sulfate precipitation will simplify extraction of proteins and is considered to be a gold standard among various precipitation methods. Therefore, optimization of ammonium sulfate precipitation can be an important functional step in protein purification. The presence of high amounts of ammonium sulphate precludes direct detection of many enzymatically active proteins including reducing sugar assays (e.g. Nelson-Somogyi, Reissig and 3,5-dinitrosalicylic acid methods) for assessing carbohydrases (e.g. laminarinase (β (1-3)-glucanohydrolase), cellulases and chitinases). In this study, a simple method was developed using laminarin infused agarose plate for the direct analysis of the ammonium sulphate precipitates from Streptomyces rimosus AFM-1. The developed method is simple and convenient that can give accurate results even in presence of ammonium sulfate in the crude precipitates. Laminarin is a translucent substrate requiring the use of a stain to visualize the zones of hydrolysis in a plate assay. A very low-cost and locally available fluorescent optical fabric brightener Tinopal CBS-X has been used as a stain to detect the zones of hydrolysis. We also report simple methods to prepare colloidal chitin and cell free supernatant in this manuscript.

Microbial Degradation of Lobster Shells to Extract Chitin Derivatives for Plant Disease Management

Biodegradation of lobster shells by chitinolytic microorganisms are an environment safe approach to utilize lobster processing wastes for chitin derivation. In this study, we report degradation activities of two microbes, "S223" and "S224" isolated from soil samples that had the highest rate of deproteinization, demineralization and chitinolysis among ten microorganisms screened. Isolates S223 and S224 had 27.3 and 103.8 protease units mg-1 protein and 12.3 and 11.2 μg ml-1 of calcium in their samples, respectively, after 1 week of incubation with raw lobster shells. Further, S223 contained 23.8 μg ml-1 of N-Acetylglucosamine on day 3, while S224 had 27.3 μg ml-1 on day 7 of incubation with chitin. Morphological observations and 16S rDNA sequencing suggested both the isolates were Streptomyces. The culture conditions were optimized for efficient degradation of lobster shells and chitinase (∼30 kDa) was purified from crude extract by affinity chromatography. The digested lobster shell extracts induced disease resistance in Arabidopsis by induction of defense related genes (PR1 > 500-fold, PDF1.2 > 40-fold) upon Pseudomonas syringae and Botrytis cinerea infection. The study suggests that soil microbes aid in sustainable bioconversion of lobster shells and extraction of chitin derivatives that could be applied in plant protection.

Genome sequence and phenotypic analysis of a first German Francisella sp. isolate (W12-1067) not belonging to the species Francisella tularensis

BACKGROUND

Francisella isolates from patients suffering from tularemia in Germany are generally strains of the species F. tularensis subsp. holarctica. To our knowledge, no other Francisella species are known for Germany. Recently, a new Francisella species could be isolated from a water reservoir of a cooling tower in Germany.

RESULTS

We identified a Francisella sp. (isolate W12-1067) whose 16S rDNA is 99% identical to the respective nucleotide sequence of the recently published strain F. guangzhouensis. The overall sequence identity of the fopA, gyrA, rpoA, groEL, sdhA and dnaK genes is only 89%, indicating that strain W12-1067 is not identical to F. guangzhouensis. W12-1067 was isolated from a water reservoir of a cooling tower of a hospital in Germany. The growth optimum of the isolate is approximately 30°C, it can grow in the presence of 4-5% NaCl (halotolerant) and is able to grow without additional cysteine within the medium. The strain was able to replicate within a mouse-derived macrophage-like cell line. The whole genome of the strain was sequenced (~1.7 mbp, 32.2% G + C content) and the draft genome was annotated. Various virulence genes common to the genus Francisella are present, but the Francisella pathogenicity island (FPI) is missing. However, another putative type-VI secretion system is present within the genome of strain W12-1067.

CONCLUSIONS

Isolate W12-1067 is closely related to the recently described F. guangzhouensis species and it replicates within eukaryotic host cells. Since W12-1067 exhibits a putative new type-VI secretion system and F. tularensis subsp. holarctica was found not to be the sole species in Germany, the new isolate is an interesting species to be analyzed in more detail. Further research is needed to investigate the epidemiology, ecology and pathogenicity of Francisella species present in Germany.

Legionella pneumophila type II secretome reveals unique exoproteins and a chitinase that promotes bacterial persistence in the lung

Type II protein secretion is critical for Legionella pneumophila infection of amoebae, macrophages, and mice. Previously, we found several enzymes to be secreted by this (Lsp) secretory pathway. To better define the L. pneumophila type II secretome, a 2D electrophoresis proteomic approach was used to compare proteins in wild-type and type II mutant supernatants. We identified 20 proteins that are type II-dependent, including aminopeptidases, an RNase, and chitinase, as well as proteins with no homology to known proteins. Because a chitinase had not been previously reported in Legionella, we determined that wild type secretes activity against both p-nitrophenyl triacetyl chitotriose and glycol chitin. An lsp mutant had a 70-75% reduction in activity, confirming the type II dependency of the secreted chitinase. Newly constructed chitinase (chiA) mutants also had approximately 75% less activity, and reintroduction of chiA restored the mutants to normal levels of activity. Although chiA mutants were not impaired for in vitro intracellular infection, they were defective upon intratracheal inoculation into the lungs of A/J mice, and antibodies against ChiA were detectable in infected animals. In contrast, mutants lacking a secreted phosphatase, protease, or one of several lipolytic enzymes were not defective in vivo. In sum, this study shows that the output of type II secretion is greater in magnitude than previously appreciated and includes previously undescribed proteins. Our data also indicate that an enzyme with chitinase activity can promote infection of a mammalian host.