Purification and characterization of a metalloprotease from Chryseobacterium indologenes Ix9a and determination of the amino acid specificity with electrospray mass spectrometry

Identification and characterization of CIM-1, a carbapenemase that adds to the family of resistance factors against last resort antibiotics

The increasing rate of carbapenem-resistant bacteria within healthcare environments is an issue of great concern that needs urgent attention. This resistance is driven by metallo-β-lactamases (MBLs), which can catalyse the hydrolysis of almost all clinically available β-lactams and are resistant to all the clinically utilized β-lactamase inhibitors. In this study, an uncharacterized MBL is identified in a multidrug resistant isolate of the opportunistic pathogen, Chryseobacterium indologenes. Sequence analysis predicts this MBL (CIM-1) to be a lipoprotein with an atypical lipobox. Characterization of CIM-1 reveals it to be a high-affinity carbapenemase with a broad spectrum of activity that includes all cephalosporins and carbapenems. Results also shown that CIM-1 is potentially a membrane-associated MBL with an uncharacterized lipobox. Using prediction tools, we also identify more potentially lipidated MBLs with non-canonical lipoboxes highlighting the necessity of further investigation of lipidated MBLs.

The role of complement in the tick cellular immune defense against the entomopathogenic fungus Metarhizium robertsii

Entomopathogenic fungi (EPF) have been widely explored for their potential in the biological control of insect pests and as an environmentally friendly alternative to acaricides for limiting tick infestation in the field. The arthropod cuticle is the main barrier against fungal infection, however, an understanding of internal defense mechanisms after EPF intrusion into the invertebrate hemocoel is still rather limited. Using an infection model of the European Lyme borreliosis vector Ixodes ricinus with the EPF Metarhizium robertsii, we demonstrated that ticks are capable of protecting themselves to a certain extent against mild fungal infections. However, tick mortality dramatically increases when the capability of tick hemocytes to phagocytose fungal conidia is impaired. Using RNAi-mediated silencing of tick thioester-containing proteins (TEPs), followed by in vitro and/or in vivo phagocytic assays, we found that C3-like complement components and α2-macroglobulin pan-protease inhibitors secreted to the hemolymph play pivotal roles in M. robertsii phagocytosis.

Chryseobacterium pennae sp. nov., isolated from poultry feather waste

A Gram-stain-negative, rod-shaped, non-motile, non-spore-forming, aerobic, yellow-pigmented bacterium was isolated from chicken feather waste collected from an abattoir in Bloemfontein, South Africa. A polyphasic taxonomy study was used to describe and name the bacterial isolate, strain 1_F178T. The 16S rRNA gene sequence analysis and sequence comparison data indicated that strain 1_F178T was a member of the genus Chryseobacterium and was closely related to Chryseobacterium jejuense (99.1%) and Chryseobacterium nakagawai (98.7%). Overall genome similarity metrics (average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity) revealed greatest similarity to the C. jejuense and C. nakagawai type strains but were below the threshold for species delineation. Genome sequencing revealed a genome size of 6.18 Mbp and a G+C content of 35.6 mol%. The major respiratory quinone and most abundant polar lipid of strain 1_F178T were menaquinone-6 and phosphatidylethanolamine, respectively. Strain 1_F178T had a typical fatty acid composition for Chryseobacterium species. On the basis of physiological, genotypic, phylogenetic and chemotaxonomic data, strain 1_F178T constitutes a novel species of Chryseobacterium, for which the name Chryseobacterium pennae sp. nov. is proposed. The type strain is 1_F178T (=LMG 30779T=KCTC 62759T).

Heterologous expression and characterisation of a keratinase produced by Chryseobacterium carnipullorum

Chryseobacterium carnipullorum 9_R23581^T, isolated from raw chicken meat, was evaluated for its potential to degrade keratin found in feathers. The focus of this study was to heterologously express and characterise a keratinolytic enzyme produced by C. carnipullorum. Chryseobacterium carnipullorum secretes proteolytic enzymes that have feather degrading capabilities during its exponential growth phase. This study concluded that the most likely main component of the keratinolytic enzymes of C. carnipullorum was peptidase M64, a serine-endopeptidase with a molecular weight in crude form of 49.46 kDa. Primers were designed on the selected gene of interest, which was amplified from the genome of C. carnipullorum (accession number NZ-FRCD01000002.1). The gene coding for peptidase M64 was further cloned, propagated and expressed in E. coli BL21 [DE3] cells. Purification was by Immobilised Metal Affinity Chromatography (IMAC). The molecular weight of the keratinase was about 50 kDa after purification while its optimum temperature and pH were 50 °C and 8.5, respectively. The activity of this keratinase was inhibited by phenylmethylsulfonyl fluoride (PMSF) and it was enhanced by the presence of divalent metal ions such as Mg²⁺ and Ca²⁺. Enzyme activity was further assayed by application to chicken feathers and observed degradation was an indication of keratinolytic potential.

Spoilage potential of psychrotrophic bacteria isolated from raw milk and the thermo-stability of their enzymes

The storage and transportation of raw milk at low temperatures promote the growth of psychrotrophic bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy products. Though many studies have been carried out on the spoilage potential of psychrotrophic bacteria and the thermo-stabilities of the enzymes they produce, further detailed studies are needed to devise an effective strategy to avoid dairy spoilage. The purpose of this study was to explore the spoilage potential of psychrotrophic bacteria from Chinese raw milk samples at both room temperature (28 °C) and refrigerated temperature (7 °C). Species of Yersinia, Pseudomonas, Serratia, and Chryseobacterium showed high proteolytic activity. The highest proteolytic activity was shown by Yersinia intermedia followed by Pseudomonas fluorescens (d). Lipolytic activity was high in isolates of Acinetobacter, and the highest in Acinetobacter guillouiae. Certain isolates showed positive β-galactosidase and phospholipase activity. Strains belonging to the same species sometimes showed markedly different phenotypic characteristics. Proteases and lipases produced by psychrotrophic bacteria retained activity after heat treatment at 70, 80, or 90 °C, and proteases appeared to be more heat-stable than lipases. For these reasons, thermo-stable spoilage enzymes produced by a high number of psychrotrophic bacterial isolates from raw milk are of major concern to the dairy industry. The results of this study provide valuable data about the spoilage potential of bacterial strains in raw milk and the thermal resistance of the enzymes they produce.

Systematic functional analysis and application of a cold-active serine protease from a novel Chryseobacterium sp

Psychrotolerant bacteria isolated from natural and artificially cold environments were screened for synthesis of cold-active protease. The strain IMDY showing the highest protease production at 5°C was selected and phylogenetic analysis revealed that IMDY as novel bacterium with Chryseobacterium soli(T) as its nearest neighbor. Classical optimization enhanced the protease production from 18U/mg to 26U/mg and the enzyme was found to be active at low temperature, activity enhanced by CaCl2, inhibited by PMSF, stable against NaCl, and its activity retained in the presence of surfactants, organic solvents and detergents. On testing, the meat tenderization, myofibril fragmentation, pH, and TBA values were favorable in IMDY-protease treated meat compared to control. SDS profiling and SEM analysis also showed tenderization in meat samples. Hence, this study proposes to consider the cold-active protease from Chryseobacterium sp. IMDY as a pertinent candidate to develop potential applications in food processing industry.

Spoilage potential of a novel group of bacteria isolated from dairy products

Abstract Cold-tolerant bacteria, also known as psychrotrophic bacteria, are notorious contaminants of milk in the refrigerated dairy food chain. These organisms, especially the pseudomonads, may produce heat-resistant enzymes that are responsible for the breakdown of proteins and lipids in milk and dairy products. Such reactions result in a variety of defects in the raw or unprocessed milk that may affect the suitability of such milk for further processing. The enzymes produced may cause defects in long-life dairy products such as cheese, butter and long-life milk. In the present study, a range of 18 yellow pigmented psychrotrophic bacteria, collectively known as flavobacteria, were isolated from local dairy products. One aim of this study was to identify these bacteria to species level using molecular techniques. A second aim was to determine the spoilage potential of these organisms based on profiles generated by the BIOLOG system (that may relate to hydrolytic enzymes produced). Of the 18 isolates, 14 belonged to the genus Chryseobacterium while 4 were identified as Empedobacter isolates. The most active spoilage organisms in this group were shown to be C. bovis, C. shigense and E. brevis. These findings illustrate that enzymatically catalysed defects in dairy products should not be attributed solely to acknowledged psychrotrophic bacteria such as the pseudomonads, but that flavobacterial species may also be actively involved.

Comparison of the growth kinetics and proteolytic activities of Chryseobacterium species and Pseudomonas fluorescens

The effect of temperature on the growth kinetics and proteolytic activity of Chryseobacterium joostei and Chryseobacterium bovis was determined during this study. The results were compared with the activities of Pseudomonas fluorescens, which is regarded to be a major food spoilage psychrotolerant microorganism. For the growth studies, cultures were incubated in nutrient broth in a temperature gradient incubator (from 9 to 50 °C) and separately at 4 °C, and the optical density was measured at different time intervals. Growth temperature profiles for each organism were constructed. For determination of proteolytic activity, the cultures were incubated in fat-free ultra-high temperature processed milk in the temperature gradient incubator for 72 h (temperature range as above). Cell-free extracts were used to determine the proteolytic activity using the azocasein method. Results of the growth studies showed that C. joostei had the ability to grow over a wider temperature range than C. bovis and P. fluorescens without being affected by changes in the temperature. For the proteolytic activity, C. joostei had significantly (p < 0.001) higher activity per milligram of protein at 15.5 °C, followed by C. bovis and P. fluorescens. The results showed that C. joostei potentially has an even greater spoilage capacity in milk on the basis of growth rate and proteolytic activity than did P. fluorescens.

Production and properties of keratinolytic proteases from three novel Gram-negative feather-degrading bacteria isolated from Brazilian soils

The keratinolytic potential and protease properties of three novel Gram-negative feather-degrading bacteria isolated from Brazilian soils was described. Aeromonas hydrophila K12, Chryseobacterium indologenes A22 and Serratia marcescens P3 were able to degrade feather meal, producing high amounts of soluble proteins and forming thiol groups. The proteases of strains K12, A22 and P3 had optimal pH of 8.0, 7.5 and 6.0, respectively; this last is an uncommon feature for bacterial keratinases. The optimal temperature was in the range 45-55°C. All three proteases were active towards azokeratin and were inhibited by EDTA, suggesting that they are keratinolytic metalloproteases. The proteolytic activity of K12 was stimulated by organic solvents and the detergent SDS, suggesting its potential application for detergent formulations and peptide synthesis. Strains A22, K12 and P3 have great potential for use in biotechnological processes involving hydrolysis of keratinous byproducts.

Immunolocalization and characterization of two novel proteases in Leishmania donovani: putative roles in host invasion and parasite development

Two novel intracellular proteases having identical molecular mass (58 kDa) were purified from virulent Indian strain of Leishmania donovani by a combination of aprotinin-agarose affinity chromatography, ion exchange chromatography and finally continuous elution electrophoresis. Both of these proteases migrate in SDS-PAGE as a single homogeneous bands suggesting monomeric nature of these proteases. The enzyme activity of one of the proteases was inhibited by serine protease inhibitor aprotinin and another one was inhibited by metalloprotease inhibitor 1, 10 phenanthroline. The purified enzymes were thus of serine protease (SP-Ld) and metalloprotease (MP-Ld) type. The optimal pH for protease activity is 8.0 and 7.5 for SP-Ld and MP-Ld respectively. The temperature optimum for SP-Ld is 28 °C and for MP-Ld is 37 °C showing their thermostability upto 60 °C. Broad substrate (both natural and synthetic) specificity and the effect of Ca2+ upon these enzymes suggested novelty of these proteases. Kinetic data indicate that SP-Ld is of trypsin like as BAPNA appears to be the best substrate and MP-Ld seems to be collagenase type as it degrades azocoll with maximum efficiency. Both immunofluorescence and immune-gold electron microscopy studies revealed that the SP-Ld is localized in the flagellar pocket as well as at the surface of the parasite, whereas MP-Ld is located extensively near the flagellar pocket region. This work also suggests that the uses of anti SP-Ld and anti MP-Ld antibodies are quite significant in interfering with the process of parasite invasion and multiplication respectively. Thus the major role of SP-Ld could be predicted in invasion process as it down regulates the phagocytic activity of macrophages, and MP-Ld appears to play important roles in parasitic development.

Keratinase production by endophytic Penicillium spp. Morsy1 under solid-state fermentation using rice straw

Among all endophytic keratinolytic fungal isolates recovered from marine soft coral Dendronephthya hemprichii, Penicillium spp. Morsy1 was selected as the hyperactive keratinolytic strain under solid substrate fermentation of different agriculture and poultry wastes. The optimization of extraction process, physicochemical parameters affecting the keratinase production in solid-state fermentation, and the purified keratinase parameters were studied. Maximum keratinase activity (1,600 U g(-1), initial dry substrate) was recovered from moldy bran with 0.1% Tween 80. The optimized production conditions were rice straw as carbon source, pH of medium 6, growth temperature 26 degrees C, initial moisture content of 80% (v/w), inoculum size of 10(5) spores ml(-1), and an average particle size of the substrate 0.6 mm (3,560 U g(-1), initial dry substrate after 5 days of fermentation). Two types of keratinase (Ahm1 and Ahm2) were purified from the culture supernatant through ammonium sulfate precipitation, DEAE-Sepharose, and gel filtration chromatography. Enzyme molecular weights were 19 kDa (Ahm1) and 40 kDa (Ahm2). The kinetic parameters of purified keratinases were optimized for the hydrolysis of azokeratin by Ahm1 (pH 7.0-8.0, stable in pH range of 6.0 to 8.0 at 50 degrees C) and Ahm2 enzymes (pH 10.0-11.0, stable in pH range of 6.0 to 11.0 at 60-65 degrees C). Whereas inhibitors of serine (phenylmethylsulfonyl fluoride) and cysteine (iodoacetamide) proteases had minor effects on both Ahm1 and Ahm2 activity, both keratinases were strongly inhibited by chelating agents EDTA and EGTA. These findings suggest that serine and cysteine residues are not involved in the catalytic mechanisms, and they are metalloproteases.

IrAM-An alpha2-macroglobulin from the hard tick Ixodes ricinus: characterization and function in phagocytosis of a potential pathogen Chryseobacterium indologenes

The universal protease inhibitors of the alpha(2)-macroglobulin (alpha(2)M) family are evolutionarily conserved constituents of innate immunity, presumably because they guard organisms against undesired proteolytic attacks of a different origin. Here, we determined the primary structure of alpha(2)-macroglobulin from the hard tick Ixodes ricinus (IrAM) by sequencing of overlapping PCR products. Predicted disulfide and glycosylation patterns, post-translational cleavage and alternative splicing within its 'bait region' demonstrate that IrAM is closely related to the alpha(2)-macroglobulin from the soft tick Ornithodoros moubata. The IrAM message is expressed in all tick developmental stages and tissues, except for the gut, and the protein was detected to be mainly present in the hemolymph. Silencing of IrAM by dsRNA interference markedly reduced the phagocytosis of a potential pathogen, Chryseobacterium indologenes, by tick hemocytes both in vitro and in vivo. In contrast, phagocytosis of the Lyme disease spirochete Borrelia burgdorferi or a commensal bacteria Staphylococcus xylosus was not affected by the IrAM knock-down. Similar results were obtained upon deactivation of all thioester proteins in tick hemolymph by methylamine. We have further demonstrated that phagocytosis of C. indologenes is dependent on an active metalloprotease secreted by the bacteria. These data indicate that interaction of tick alpha(2)-macroglobulin with a protease of an invading pathogen is linked with cellular immune response.

Purification and characterization of three novel keratinolytic metalloproteases produced by Chryseobacterium indologenes TKU014 in a shrimp shell powder medium

A protease-producing bacterium was isolated and identified as Chryseobacterium indologenes TKU014. The optimized condition for protease production was found when the culture was shaken at 30 degrees C for one day in 50 mL of medium containing 0.5% shrimp shell powder (w/v), 0.1% K(2)HPO(4), and 0.05% MgSO(4).7H(2)O. Three extracellular proteases (P1, P2, and P3) were purified from culture by DEAE-Sepharose and Phenyl Sepharose chromatography. Three enzymes all showed activities of keratinase and elastase with molecular weights of 56, 40, 40 kDa, respectively. The inhibitory effect of metal chelator EDTA and Zn-specific chelator 1,10-phenanthroline characterized three enzymes as Zn-metalloproteases. Peptide mass fingerprints of P1, P2, and P3 were determined by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Similarity search in the NCBI non-redundant protein sequence database revealed that three enzymes exhibited no significant homology to any other reported microbial peptides. Therefore, P1, P2, and P3 are most likely novel proteins.

Purification and properties of a keratinolytic metalloprotease from Microbacterium sp

AIMS

This study was developed to purify and to characterize a keratinolytic protease from the bacterium Microbacterium sp. strain kr10.

METHODS AND RESULTS

Enzyme purification was carried out by sequential liquid chromatography on Sephadex G-100 and Q-Sepharose columns. The purification was about 255-fold, with a yield of 34%, as determined with azocasein as substrate. The molecular weight of the enzyme was estimated as 42,000 Da by SDS-PAGE. The enzyme had pH and temperature optima of 7.5 and 50 degrees C respectively. This keratinase was inhibited by EDTA and 1,10-phenanthroline, and analysis of metal content indicates that Zn(2+) and Mg(2+) are present. A 2(2) factorial design was developed to investigate the effect of keratinase and mercaptoacetate concentration on feather keratinolysis. Statistical analysis showed that both variables have a significant effect on hydrolysis of keratin.

CONCLUSIONS

A new keratinase produced by Microbacterium sp. was purified and characterized.

SIGNIFICANCE AND IMPACT OF THE STUDY

This keratinolytic enzyme offers an interesting potential for the hydrolysis of keratin wastes to be used as feed supplement or bioconversion to added-value products.

A comparison of Chryseobacterium indologenes pathogenicity to the soft tick Ornithodoros moubata and hard tick Ixodes ricinus

A yellow-pigmented Gram-negative bacterium, Chryseobacterium indologenes, was found in the gut contents of about 65% of soft ticks Ornithodoros moubata from a perishing laboratory colony. The isolated putative pathogen, C. indologenes, was susceptible to cotrimoxazol and addition of this antibiotic (Biseptol 480) to the blood meal significantly decreased the tick mortality rate. The artificial infection of healthy O. moubata by membrane feeding on blood contaminated with C. indologenes was lethal to all ticks at concentrations 10(6) bacteria/ml. On the contrary, a similar infection dose applied to the hard tick Ixodes ricinus by capillary feeding did not cause significant mortality. Examination of guts dissected from infected O. moubata and I. ricinus revealed that C. indologenes was exponentially multiplied in the soft tick but were completely cleared from the gut of the hard ticks within 1 day. In both tick species, C. indologenes were found to penetrate from the gut into the hemocoel. The phagocytic activity of hemocytes from both tick species was tested by intrahaemocoelic microinjection of C. indologenes and evaluated by indirect fluorescent microscopy using antibodies raised against whole bacteria. Hemocytes from both tick species displayed significant phagocytic activity against C. indologenes. All O. moubata injected with C. indologenes died within 3 days, whereas the increase of the mortality rate of I. ricinus was insignificant. Our results indicate that hard ticks possess much more efficient defense system against infection with C. indologenes than the soft ticks. Thus, C. indologenes infection has the potential to be a relevant comparative model for the study of tick immune reactions to transmitted pathogens.

Characterization of excretory/secretory endopeptidase and metallo-aminopeptidases from Taenia crassiceps metacestodes

Cysticercosis is caused by Taenia spp. metacestodes, which must survive in the host tissues to complete their life cycle. Their survival depends on their control of host immune responses. Because many parasites use proteases to modulate host responses, we examined culture media from Taenia crassiceps metacestodes for protease activity using peptide substrates. We identified prominent aminopeptidase activity at neutral pH, which was inhibited by chelating agents and partially inhibited by the aminopeptidase inhibitor, bestatin. Endopeptidase substrates were optimally cleaved at slightly acidic pH and endopeptidase activity was inhibited by cysteine protease inhibitors. Gel filtration FPLC and subsequent visualization by silver staining revealed a metallo-aminopeptidase of molecular weight 21 kDa and cysteine proteases of Mr 70 and 64 kDA. Recombinant IL-2 was digested when incubated with parasite culture supernatants, but not with control media. IL-2 degradation was completely inhibited by 1,10 phenanthroline and partially inhibited by bestatin, suggesting that a metallo-aminopeptidase was responsible. Incubation of human IgG with culture supernatants resulted in complete degradation of IgG, which was blocked by cysteine protease inhibitors. These observations demonstrate that Taenia spp. metacestodes secrete a number of proteolytic enzymes, which may target molecules from the host immune system and assist in evasion of the host immune response.

Characterization of a new keratinolytic bacterium that completely degrades native feather keratin

A novel feather-degrading microorganism was isolated from poultry waste, producing a high keratinolytic activity when cultured on broth containing native feather. Complete feather degradation was achieved during cultivation. The bacterium presents potential use for biotechnological processes involving keratin hydrolysis. Chryseobacterium sp. strain kr6 was identified based on morphological and biochemical tests and 16S rRNA sequencing. The bacterium presented optimum growth at pH 8.0 and 30 degrees C; under these conditions, maximum feather-degrading activity was also achieved. Maximum keratinase production was reached at 25 degrees C, while concentration of soluble protein was similar at both 25 and 30 degrees C. Reduction of disulfide bridges was also observed, increasing with cultivation time. The keratinase of strain kr6 was active on azokeratin and azocasein as substrates, and presented optimum pH and temperature of 7.5 and 55 degrees C, respectively. The keratinase activity was inhibited by 1,10-phenanthroline, EDTA, Hg(2+), and Cu(2+) and stimulated by Ca(2+).