A diverse range of bacterial and eukaryotic chitinases hydrolyzes the LacNAc (Galβ1-4GlcNAc) and LacdiNAc (GalNAcβ1-4GlcNAc) motifs found on vertebrate and insect cells

Exploring roles of the chitinase ChiC in modulating Pseudomonas aeruginosa virulence phenotypes

Chitinases are ubiquitous enzymes involved in biomass degradation and chitin turnover in nature. Pseudomonas aeruginosa (PA), an opportunistic human pathogen, expresses ChiC, a secreted glycoside hydrolase 18 family chitinase. Despite speculation about ChiC's role in PA disease pathogenesis, there is scant evidence supporting this hypothesis. Since PA cannot catabolize chitin, we investigated the potential function(s) of ChiC in PA pathophysiology. Our findings show that ChiC exhibits activity against both insoluble (α- and β-chitin) and soluble chitooligosaccharides. Enzyme kinetics toward (GlcNAc)4 revealed a kcat of 6.50 s-1 and a KM of 1.38 mM, the latter remarkably high for a canonical chitinase. In our label-free proteomics investigation, ChiC was among the most abundant proteins in the Pel biofilm, suggesting a potential contribution to PA biofilm formation. Using an intratracheal challenge model of PA pneumonia, the chiC::ISphoA/hah transposon insertion mutant paradoxically showed slightly increased virulence compared to the wild-type parent strain. Our results indicate that ChiC is a genuine chitinase that contributes to a PA pathoadaptive pathway.IMPORTANCEIn addition to performing chitin degradation, chitinases from the glycoside hydrolase 18 family have been found to play important roles during pathogenic bacterial infection. Pseudomonas aeruginosa is an opportunistic pathogen capable of causing pneumonia in immunocompromised individuals. Despite not being able to grow on chitin, the bacterium produces a chitinase (ChiC) with hitherto unknown function. This study describes an in-depth characterization of ChiC, focusing on its potential contribution to the bacterium's disease-causing ability. We demonstrate that ChiC can degrade both polymeric chitin and chitooligosaccharides, and proteomic analysis of Pseudomonas aeruginosa biofilm revealed an abundance of ChiC, hinting at a potential role in biofilm formation. Surprisingly, a mutant strain incapable of ChiC production showed higher virulence than the wild-type strain. While ChiC appears to be a genuine chitinase, further investigation is required to fully elucidate its contribution to Pseudomonas aeruginosa virulence, an important task given the evident health risk posed by this bacterium.

Veterinary bacteriology in Denmark from the 1880s to 2022

This paper gives an account of the history of veterinary bacteriology including clinical veterinary bacteriology as well as the area of veterinary public health in Denmark from the 1880s to 2022. We describe key persons, including B. Bang, C.O. Jensen, K.A. Jensen and others who made important contributions to the development of these areas of microbiological expertise, and we discuss how challenges ranging from bovine tuberculosis to bacterial antimicrobial resistance have been met. Further, we describe progress in research on important bacterial pathogens both with regard to animal clinical aspects and zoonotic food-related aspects. Finally, we describe current issues in relation to One Health and research organization.

Chitinases as key virulence factors in microbial pathogens: Understanding their role and potential as therapeutic targets

Chitinases are crucial for the survival of bacterial and fungal pathogens both during host infection and outside the host in the environment. Chitinases facilitate adhesion onto host cells, act as virulence factors during infection, and provide protection from the host immune system, making them crucial factors in the survival of microbial pathogens. Understanding the mechanisms behind chitinase action is beneficial to design novel therapeutics to control microbial infections. This review explores the role of chitinases in the pathogenesis of bacterial, fungal, and viral infections. The mechanisms underlying the action of chitinases of bacterial, fungal, and viral pathogens in host cells are thoroughly reviewed. The evolutionary relationships between chitinases of various bacterial, fungal, and viral pathogens are discussed to determine their involvement in processes, such as adhesion and host immune system modulation. Gaining a better understanding of the distribution and activity of chitinases in these microbial pathogens can help elucidate their role in the invasion and infection of host cells.

Bacterial Chitinases and Their Role in Human Infection

It has been widely appreciated that numerous bacterial species express chitinases for the purpose of degrading environmental chitin. However, chitinases and chitin-binding proteins are also expressed by pathogenic bacterial species during infection even though mammals do not produce chitin. Alternative molecular targets are therefore likely present within the host. Here, we will describe our current understanding of chitinase/chitin-binding proteins as virulence factors that promote bacterial colonization and infection. The targets of these chitinases in the host have been shown to include immune system components, mucins, and surface glycans. Bacterial chitinases have also been shown to interact with other microorganisms, targeting the peptidoglycan or chitin in the bacterial and fungal cell wall, respectively. This review highlights that even though the name "chitinase" implies activity toward chitin, chitinases can have a wide diversity of targets, including ones relevant to host infection. Chitinases may therefore be useful as a target of future anti-infective therapeutics.

GH18 family glycoside hydrolase Chitinase A of Salmonella enhances virulence by facilitating invasion and modulating host immune responses

Salmonella is a facultative intracellular pathogen that has co-evolved with its host and has also developed various strategies to evade the host immune responses. Salmonella recruits an array of virulence factors to escape from host defense mechanisms. Previously chitinase A (chiA) was found to be upregulated in intracellular Salmonella. Although studies show that several structurally similar chitinases and chitin-binding proteins (CBP) of many human pathogens have a profound role in various aspects of pathogenesis, like adhesion, virulence, and immune evasion, the role of chitinase in the intravacuolar pathogen Salmonella has not yet been elucidated. Therefore, we made chromosomal deletions of the chitinase encoding gene (chiA) to study the role of chitinase of Salmonella enterica in the pathogenesis of the serovars, Typhimurium, and Typhi using in vitro cell culture model and two different in vivo hosts. Our data indicate that ChiA removes the terminal sialic acid moiety from the host cell surface, and facilitates the invasion of the pathogen into the epithelial cells. Interestingly we found that the mutant bacteria also quit the Salmonella-containing vacuole and hyper-proliferate in the cytoplasm of the epithelial cells. Further, we found that ChiA aids in reactive nitrogen species (RNS) and reactive oxygen species (ROS) production in the phagocytes, leading to MHCII downregulation followed by suppression of antigen presentation and antibacterial responses. Notably, in the murine host, the mutant shows compromised virulence, leading to immune activation and pathogen clearance. In continuation of the study in C. elegans, Salmonella Typhi ChiA was found to facilitate bacterial attachment to the intestinal epithelium, intestinal colonization, and persistence by downregulating antimicrobial peptides. This study provides new insights on chitinase as an important and novel virulence determinant that helps in immune evasion and increased pathogenesis of Salmonella.

Chitinases and chitin-binding proteins have been implicated in the pathogenesis of several human pathogens associated with the mucosal barrier. Interestingly, chitinases from the major enteric pathogen, Salmonella enterica, were reported to be upregulated during macrophage and epithelial cell infection. Although Salmonella Chitinase ChiA (encoded by STM14_0022) shares sequence similarity with the pathogenic chitinases, its role as a virulence determinant remained obscured. Here we aim to investigate the role of chitinase in the context of Salmonella pathogenesis using cell culture, mouse, and nematode models. We found that Salmonella requires ChiA to remodel the intestinal epithelium and access the host system. In the phagocytes, chitinase-mediated upregulation of nitric oxide (NO) leads to inhibition of MHC-I bound antigen presentation and CD8⁺ T cell proliferation. Furthermore, the absence of ChiA impairs bacterial adhesion and colonization in vivo. During the systemic phase in the murine host, Salmonella Typhimurium chitinase prevents immune activation and antimicrobial responses. Additionally, in the Caenorhabditis elegans, Salmonella Typhi chitinase promotes bacterial attachment to the intestinal epithelium and enhances pathogen colonization and persistence in the intestine by downregulating the antimicrobial peptides SPP1 and ABF2. In conclusion, our study provides novel insights into the role of Salmonella chitinase as a novel virulence factor.

Salmonella enterica serovar Typhimurium chitinases modulate the intestinal glycome and promote small intestinal invasion

Salmonella enterica serovar Typhimurium (S. Typhimurium) is one of the leading causes of food-borne illnesses worldwide. To colonize the gastrointestinal tract, S. Typhimurium produces multiple virulence factors that facilitate cellular invasion. Chitinases have been recently emerging as virulence factors for various pathogenic bacterial species, and the S. Typhimurium genome contains two annotated chitinases: STM0018 (chiA) and STM0233. However, the role of these chitinases during S. Typhimurium pathogenesis is unknown. The putative chitinase STM0233 has not been studied previously, and only limited data exists on ChiA. Chitinases typically hydrolyze chitin polymers, which are absent in vertebrates. However, chiA expression was detected in infection models and purified ChiA cleaved carbohydrate subunits present on mammalian surface glycoproteins, indicating a role during pathogenesis. Here, we demonstrate that expression of chiA and STM0233 is upregulated in the mouse gut and that both chitinases facilitate epithelial cell adhesion and invasion. S. Typhimurium lacking both chitinases showed a 70% reduction in invasion of small intestinal epithelial cells in vitro. In a gastroenteritis mouse model, chitinase-deficient S. Typhimurium strains were also significantly attenuated in the invasion of small intestinal tissue. This reduced invasion resulted in significantly delayed S. Typhimurium dissemination to the spleen and the liver, but chitinases were not required for systemic survival. The invasion defect of the chitinase-deficient strain was rescued by the presence of wild-type S. Typhimurium, suggesting that chitinases are secreted. By analyzing N-linked glycans of small intestinal cells, we identified specific N-acetylglucosamine-containing glycans as potential extracellular targets of S. Typhimurium chitinases. This analysis also revealed a differential abundance of Lewis X/A-containing glycans that is likely a result of host cell modulation due to the detection of S. Typhimurium chitinases. Similar glycomic changes elicited by chitinase deficient strains indicate functional redundancy of the chitinases. Overall, our results demonstrate that S. Typhimurium chitinases contribute to intestinal adhesion and invasion through modulation of the host glycome.

Engineering the ligand specificity of the human galectin-1 by incorporation of tryptophan analogs

Galectin-1 is a β-galactoside-binding lectin with manifold biological functions. A single tryptophan residue (W68) in its carbohydrate binding site plays a major role in ligand binding and is highly conserved among galectins. To fine tune galectin-1 specificity, we introduced several non-canonical tryptophan analogs at this position of human galectin-1 and analyzed the resulting variants using glycan microarrays. Two variants containing 7-azatryptophan and 7-fluorotryptophan showed a reduced affinity for 3'-sulfated oligosaccharides. Their interaction with different ligands was further analyzed by fluorescence polarization competition assay. Using molecular modeling we provide structural clues that the change in affinities comes from modulated interactions and solvation patterns. Thus, we show that the introduction of subtle atomic mutations in the ligand binding site of galectin-1 is an attractive approach for fine-tuning its interactions with different ligands.

Activity of CcpA-Regulated GH18 Family Glycosyl Hydrolases That Contributes to Nutrient Acquisition and Fitness in Enterococcus faecalis

The ability of Enterococcus faecalis to colonize host anatomical sites is dependent on its adaptive response to host conditions. Three glycosyl hydrolase gene clusters, each belonging to glycosyl hydrolase family 18 (GH18) (ef0114, ef0361, and ef2863), in E. faecalis were previously found to be upregulated under glucose-limiting conditions. The GH18 catalytic domain is present in proteins that are classified as either chitinases or β-1,4 endo-β-N-acetylglucosaminidases (ENGases) based on their β-1,4 endo-N-acetyl-β-d-glucosaminidase activity, and ENGase activity is commonly associated with cleaving N-linked glycoprotein, an abundant glycan structure on host epithelial surfaces. Here, we show that all three hydrolases are negatively regulated by the transcriptional regulator carbon catabolite protein A (CcpA). Additionally, we demonstrate that a constitutively active CcpA variant represses the expression of CcpA-regulated genes irrespective of glucose availability. Previous studies showed that the GH18 catalytic domains of EndoE (EF0114) and EfEndo18A (EF2863) were capable of deglycosylating RNase B, a model high-mannose-type glycoprotein. However, it remained uncertain which glycosidase is primarily responsible for the deglycosylation of high-mannose-type glycoproteins. In this study, we show by mutation analysis as well as a dose-dependent analysis of recombinant protein expression that EfEndo18A is primarily responsible for deglycosylating high-mannose glycoproteins and that the glycans removed by EfEndo18A support growth under nutrient-limiting conditions in vitro. In contrast, IgG is representative of a complex-type glycoprotein, and we demonstrate that the GH18 domain of EndoE is primarily responsible for the removal of this glycan decoration. Finally, our data highlight the combined contribution of glycosidases to the virulence of E. faecalis in vivo.

Metabolism of Poly-β1,4-N-Acetylglucosamine Substrates and Importation of N-Acetylglucosamine and Glucosamine by Enterococcus faecalis

The ability of Enterococcus faecalis to use a variety of carbon sources enables colonization at various anatomic sites within a mammalian host. N-Acetylglucosamine (GlcNAc) is one of the most abundant natural sugars and provides bacteria with a source of carbon and nitrogen when metabolized. N-Acetylglucosamine is also a component of bacterial peptidoglycan, further highlighting the significance of N-acetylglucosamine utilization. In this study, we show that CcpA-regulated enzymes are required for growth on the poly-β1,4-linked GlcNAc substrate, chitopentaose (β1,4-linked GlcNAc₅). We also show that EF0114 (EndoE) is required for growth on chitobiose (β1,4-linked GlcNAc₂) and that the GH20 domain of EndoE is required for the conversion of GlcNAc₂ to N-acetylglucosamine. GlcNAc is transported into the cell via two separate phosphotransferase system (PTS) complexes, either the PTS IICBA encoded by ef1516 (nagE) or the Mpt glucose/mannose permease complex (MptBACD). The Mpt PTS is also the primary glucosamine transporter. In order for N-acetylglucosamine to be utilized as a carbon source, phosphorylated N-acetylglucosamine (GlcNAc-6-P) must be deacetylated, and here, we show that this activity is mediated by EF1317 (an N-acetylglucosamine-6-phosphate deacetylase; NagA homolog), as a deletion of ef1317 is unable to grow on GlcNAc as the carbon source. Deamination of glucosamine to fructose-6-phosphate is required for entry into glycolysis, and we show that growth on glucosamine is dependent on EF0466 (a glucosamine-6-phosphate deaminase; NagB homolog). Collectively, our data highlight the chitinolytic machinery required for breaking down exogenous chitinous substrates, as well as the uptake and cytosolic enzymes needed for metabolizing N-acetylglucosamine. IMPORTANCE Enterococcus faecalis causes life-threatening health care-associated infections in part due to its intrinsic and acquired antibiotic resistance, its ability to form biofilms, and its nutrient versatility. Alternative nutrient acquisition systems are key factors that contribute to enterococcal colonization at biologically unique host anatomic sites. Although E. faecalis can metabolize an array of carbon sources, little is known of how this bacterium acquires these secondary nutrient sources in mammalian hosts. Our research identifies the glycosidase machinery required for degrading exogenous chitinous substrates into N-acetylglucosamine monomers for transport and metabolism of one of the most abundant naturally occurring sugars, N-acetylglucosamine. Disrupting the function of this N-acetylglucosamine acquisition pathway may lead to new treatments against multidrug-resistant enterococcal infections.

The fish pathogen Aliivibrio salmonicida LFI1238 can degrade and metabolize chitin despite major gene loss in the chitinolytic pathway

The fish pathogen Aliivibrio (Vibrio) salmonicida LFI1238 is thought to be incapable of utilizing chitin as a nutrient source since approximately half of the genes representing the chitinolytic pathway are disrupted by insertion sequences. In the present study, we combined a broad set of analytical methods to investigate this hypothesis. Cultivation studies revealed that Al. salmonicida grew efficiently on N-acetylglucosamine (GlcNAc) and chitobiose ((GlcNAc)₂), the primary soluble products resulting from enzymatic chitin hydrolysis. The bacterium was also able to grow on chitin particles, albeit at a lower rate compared to the soluble substrates. The genome of the bacterium contains five disrupted chitinase genes (pseudogenes) and three intact genes encoding a glycoside hydrolase family 18 (GH18) chitinase and two auxiliary activity family 10 (AA10) lytic polysaccharide monooxygenases (LPMOs). Biochemical characterization showed that the chitinase and LPMOs were able to depolymerize both α- and β-chitin to (GlcNAc)₂ and oxidized chitooligosaccharides, respectively. Notably, the chitinase displayed up to 50-fold lower activity compared to other well-studied chitinases. Deletion of the genes encoding the intact chitinolytic enzymes showed that the chitinase was important for growth on β-chitin, whereas the LPMO gene-deletion variants only showed minor growth defects on this substrate. Finally, proteomic analysis of Al. salmonicida LFI1238 growth on β-chitin showed expression of all three chitinolytic enzymes, and intriguingly also three of the disrupted chitinases. In conclusion, our results show that Al. salmonicida LFI1238 can utilize chitin as a nutrient source and that the GH18 chitinase and the two LPMOs are needed for this ability. IMPORTANCE The ability to utilize chitin as a source of nutrients is important for the survival and spread of marine microbial pathogens in the environment. One such pathogen is Aliivibrio (Vibrio) salmonicida, the causative agent of cold water vibriosis. Due to extensive gene decay, many key enzymes in the chitinolytic pathway have been disrupted, putatively rendering this bacterium incapable of chitin degradation and utilization. In the present study we demonstrate that Al. salmonicida can degrade and metabolize chitin, the most abundant biopolymer in the ocean. Our findings shed new light on the environmental adaption of this fish pathogen.

Glycan Array Technology

Glycan (or carbohydrate) arrays have become an essential tool in glycomics, providing fast and high-throughput data on protein-carbohydrate interactions with small amounts of carbohydrate ligands. The general concepts of glycan arrays have been adopted from other microarray technologies such as those used for nucleic acid and proteins. However, carbohydrates have presented their own challenges, in particular in terms of access to glycan probes, linker attachment chemistries and analysis, which will be reviewed in this chapter. As more and more glycan probes have become available through chemical and enzymatic synthesis and robust linker chemistries have been developed, the applications of glycan arrays have dramatically increased over the past 10 years, which will be illustrated with recent examples.

Effect of Noncanonical Amino Acids on Protein-Carbohydrate Interactions: Structure, Dynamics, and Carbohydrate Affinity of a Lectin Engineered with Fluorinated Tryptophan Analogs

Protein–carbohydrate interactions play crucial roles in biology. Understanding and modifying these interactions is of major interest for fighting many diseases. We took a synthetic biology approach and incorporated noncanonical amino acids into a bacterial lectin to modulate its interactions with carbohydrates. We focused on tryptophan, which is prevalent in carbohydrate binding sites. The exchange of the tryptophan residues with analogs fluorinated at different positions resulted in three distinctly fluorinated variants of the lectin from Ralstonia solanacearum. We observed differences in stability and affinity toward fucosylated glycans and rationalized them by X-ray and modeling studies. While fluorination decreased the aromaticity of the indole ring and, therefore, the strength of carbohydrate–aromatic interactions, additional weak hydrogen bonds were formed between fluorine and the ligand hydroxyl groups. Our approach opens new possibilities to engineer carbohydrate receptors.

A chitinase is required for Xylella fastidiosa colonization of its insect and plant hosts

Xylella fastidiosa colonizes the xylem network of host plant species as well as the foregut of its required insect vectors to ensure efficient propagation. Disease management strategies remain inefficient due to a limited comprehension of the mechanisms governing both insect and plant colonization. It was previously shown that X. fastidiosa has a functional chitinase (ChiA), and that chitin likely serves as a carbon source for this bacterium. We expand on that research, showing that a chiA mutant strain is unable to grow on chitin as the sole carbon source. Quantitative PCR assays allowed us to detect bacterial cells in the foregut of vectors after pathogen acquisition; populations of the wild-type and complemented mutant strain were both significantly larger than the chiA mutant strain 10 days, but not 3 days, post acquisition. These results indicate that adhesion of the chiA mutant strain to vectors may not be impaired, but that cell multiplication is limited. The mutant was also affected in its transmission by vectors to plants. In addition, the chiA mutant strain was unable to colonize host plants, suggesting that the enzyme has other substrates associated with plant colonization. Lastly, ChiA requires other X. fastidiosa protein(s) for its in vitro chitinolytic activity. The observation that the chiA mutant strain is not able to colonize plants warrants future attention to be paid to the substrates for this enzyme.

Draft Genome Sequence of Chromobacterium subtsugae MWU12-2387 Isolated from a Wild Cranberry Bog in Truro, Massachusetts

Chromobacterium subtsugae MWU12-2387 was isolated from the rhizosphere of cranberry plants. While it is unknown what environmental role these bacteria play in bog soils, they hold potential as biological control agents against nematodes and insect pests. Potential virulence genes were identified, including the violacein synthesis pathway, siderophores, and several chitinases.

Molecular Basis for Recognition of the Cancer Glycobiomarker, LacdiNAc (GalNAc[β1→4]GlcNAc), by Wisteria floribunda Agglutinin

Aberrant glycosylation and the overexpression of specific carbohydrate epitopes is a hallmark of many cancers, and tumor-associated oligosaccharides are actively investigated as targets for immunotherapy and diagnostics. Wisteria floribunda agglutinin (WFA) is a legume lectin that recognizes terminal N-acetylgalactosaminides with high affinity. WFA preferentially binds the disaccharide LacdiNAc (β-d-GalNAc-[1→4]-d-GlcNAc), which is associated with tumor malignancy in leukemia, prostate, pancreatic, ovarian, and liver cancers and has shown promise in cancer glycobiomarker detection. The mechanism of specificity for WFA recognition of LacdiNAc is not fully understood. To address this problem, we have determined affinities and structure of WFA in complex with GalNAc and LacdiNAc. Affinities toward Gal, GalNAc, and LacdiNAc were measured via surface plasmon resonance, yielding K_D values of 4.67 × 10^-4 m, 9.24 × 10^-5 m, and 5.45 × 10^-6 m, respectively. Structures of WFA in complex with LacdiNAc and GalNAc have been determined to 1.80-2.32 Å resolution. These high resolution structures revealed a hydrophobic groove complementary to the GalNAc and, to a minor extent, to the back-face of the GlcNAc sugar ring. Remarkably, the contribution of this small hydrophobic surface significantly increases the observed affinity for LacdiNAc over GalNAc. Tandem MS sequencing confirmed the presence of two isolectin forms in commercially available WFA differing only in the identities of two amino acids. Finally, the WFA carbohydrate binding site is similar to a homologous lectin isolated from Vatairea macrocarpa in complex with GalNAc, which, unlike WFA, binds not only αGalNAc but also terminal Ser/Thr O-linked αGalNAc (Tn antigen).

Glycan Arrays: From Basic Biochemical Research to Bioanalytical and Biomedical Applications

A major branch of glycobiology and glycan-focused biomedicine studies the interaction between carbohydrates and other biopolymers, most importantly, glycan-binding proteins. Today, this research into glycan-biopolymer interaction is unthinkable without glycan arrays, tools that enable high-throughput analysis of carbohydrate interaction partners. Glycan arrays offer many applications in basic biochemical research, for example, defining the specificity of glycosyltransferases and lectins such as immune receptors. Biomedical applications include the characterization and surveillance of influenza strains, identification of biomarkers for cancer and infection, and profiling of immune responses to vaccines. Here, we review major applications of glycan arrays both in basic and applied research. Given the dynamic nature of this rapidly developing field, we focus on recent findings.

The Draft Genome Sequence of the Yersinia entomophaga Entomopathogenic Type Strain MH96T

Here we report the draft genome of Yersinia entomophaga type strain MH96T. The genome shows 93.8% nucleotide sequence identity to that of Yersinia nurmii type strain APN3a-cT, and comprises a single chromosome of approximately 4,275,531 bp. In silico analysis identified that, in addition to the previously documented Y. entomophaga Yen-TC gene cluster, the genome encodes a diverse array of toxins, including two type III secretion systems, and five rhs-associated gene clusters. As well as these multicomponent systems, several orthologs of known insect toxins, such as VIP2 toxin and the binary toxin PirAB, and distant orthologs of some mammalian toxins, including repeats-in-toxin, a cytolethal distending toxin, hemolysin-like genes and an adenylate cyclase were identified. The genome also contains a large number of hypothetical proteins and orthologs of known effector proteins, such as LopT, as well as genes encoding a wide range of proteolytic determinants, including metalloproteases and pathogen fitness determinants, such as genes involved in iron metabolism. The bioinformatic data derived from the current in silico analysis, along with previous information on the pathobiology of Y. entomophaga against its insect hosts, suggests that a number of these virulence systems are required for survival in the hemocoel and incapacitation of the insect host.

Characterization of two Listeria innocua chitinases of different sizes that were expressed in Escherichia coli

Two putative chitinase genes, lin0153 and lin1996, from the nonpathogenic bacterium Listeria innocua were expressed in Escherichia coli, and the gene products were characterized. The genes were close homologs of chitinases from the pathogenic bacterium Listeria monocytogenes, in which chitinases and chitin-binding proteins play important roles in pathogenesis in mice-infection models. The purified recombinant enzymes that are different in size, LinChi78 (lin0153 product) and LinChi35 (lin1996 product)-with molecular masses of 82 and 38 kDa, including vector-derived additional sequences, respectively-exhibited optimum catalytic activity under neutral and acidic conditions at 50 °C, respectively, and were stable over broad pH (4-11) and temperature (4-40 °C) ranges. LinChi35 displayed higher k cat and K M values for 4-nitrophenyl N,N-diacetyl-β-D-chitobioside [4NP-(GlcNAc)2] than LinChi78. Both enzymes produced primarily dimers from colloidal chitin as a substrate. However, LinChi78 and LinChi35 could hydrolyze oligomeric substrates in a processive exo- and nonprocessive endo-manner, respectively, and showed different reactivity toward oligomeric substrates. Both enzymes could bind chitin beads but were different in their binding ability toward crystalline α-chitin and cellulose. The structure-function relationships of these chitinases are discussed in reference to other bacterial chitinases.

Draft Genome Sequences of Three Chromobacterium subtsugae Isolates from Wild and Cultivated Cranberry Bogs in Southeastern Massachusetts

Chromobacterium subtsugae was isolated from cranberry bogs in Massachusetts. While it is unknown what environmental role these bacteria play in bog soils, they hold potential as biological control agents against the larvae of insect pests. Potential virulence genes were identified, including the violacein synthesis pathway, siderophores, and several chitinases.

Draft Genome Sequence of Chromobacterium vaccinii, a Potential Biocontrol Agent against Mosquito (Aedes aegypti) Larvae

Chromobacterium vaccinii has been isolated only from cranberry bogs in Massachusetts. While it is unknown what role these bacteria play in their natural environments, they hold potential as biological control agents against the larvae of insect pests. Potential virulence genes were identified, including the violacein synthesis pathway, siderophores, and chitinases.

Effects of Listeria monocytogenes EGD-e and Salmonella enterica ser. Typhimurium LT2 chitinases on intracellular survival in Dictyostelium discoideum and mammalian cell lines

Some bacterial pathogens produce chitinases as virulence factors during host infection. The molecular target of such enzymes in non-chitinous hosts remains uncertain. We studied the importance of Listeria monocytogenes EGD-e and Salmonella enterica ser. Typhimurium LT2 chitinases for intracellular survival in Dictyostelium discoideum, and for Salmonella, also infection of mammalian cell lines, and a mouse model. The Salmonella chitinase did not contribute significantly to infection of D. discoideum, mammalian cell lines or mice. However, survival in D. discoideum was clearly reduced for Listeria mutants deficient of ChiB (8-fold) or deficient of both ChiA and ChiB (22-fold). Our findings suggest that chitinases from the two species play different roles in virulence.