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PubMed2006

Characterization of a recombinantly expressed proteinase K-like enzyme from a psychrotrophic Serratia sp.

The gene encoding a peptidase that belongs to the proteinase K family of serine peptidases has been identified from a psychrotrophic Serratia sp., and cloned and expressed in Escherichia coli. The gene has 1890 base pairs and encodes a precursor protein of 629 amino acids with a theoretical molecular mass of 65.5 kDa. Sequence analysis suggests that the peptidase consists of a prepro region, a catalytic domain and two C-terminal domains. The enzyme is recombinantly expressed as an active approximately 56 kDa peptidase and includes both C-terminal domains. Purified enzyme is converted to the approximately 34 kDa form by autolytic cleavage when incubated at 50 degrees C for 30 min, but retains full activity. In the present work, the Serratia peptidase (SPRK) is compared with the family representative proteinase K (PRK) from Tritirachium album Limber. Both enzymes show a relatively high thermal stability and a broad pH stability profile. SPRK possess superior stability towards SDS at 50 degrees C compared to PRK. On the other hand, SPRK is considerably more labile to removal of calcium ions. The activity profiles against temperature and pH differ for the two enzymes. SPRK shows both a broader pH optimum as well as a higher temperature optimum than PRK. Analysis of the catalytic properties of SPRK and PRK using the synthetic peptide succinyl-Ala-Ala-Pro-Phe-pNA as substrate showed that SPRK possesses a 3.5-4.5-fold higher kcat at the temperature range 12-37 degrees C, but a fivefold higher Km results in a slightly lower catalytic efficiency (kcat/Km) of SPRK compared to PRK.

Amino Acid Sequence↗
PubMed1977

Resistance plasmid transfer by Serratia marcescens in urine.

Resistance plasmids were transferred in urine from a multi-drug-resistant Serratia marcescens to Escherichia coli. Transfer of resistance to kanamycin, tetracycline, chloramphenicol, streptomycin, ampicillin, and carbenicillin occurred readily after 4 h of incubation at room temperature (25 degrees C). The urinary catheter collection bag is postulated as a potential site for extraintestinal resistance plasmid transfer in the Enterobacteriaceae, especially for pathogens such as Serratia, which do not frequently colonize the intestinal tract.

Anti-Bacterial Agents↗
PubMed1979

LY127935, a new beta-lactam antibiotic, versus Proteus, Klebsiella, Serratia, and Pseudomonas.

One hundred eight clinical isolates of Proteus, Klebsiella, Serratia, and Pseudomonas spp. were tested in vitro against LY127935, cefamandole, cefoxitin, ticarcillin, carbenicillin, gentamicin, tobramycin, and amikacin by broth microdilution. The activities of LY127935 were greater than or equal to those of the other antimicrobial agents against Proteus vulgaris, Klebsiella pneumoniae, and Serratia marcescens. Inhibitions were greatest, however, for ticarcillin and carbenicillin versus Proteus morganii and gentamicin versus Pseudomonas aeruginosa.

Anti-Bacterial Agents↗
PubMed1992

Characterization of the chromosomal aac(6')-Ic gene from Serratia marcescens.

The DNA sequence of the chromosomal aac(6')-Ic gene from Serratia marcescens, which had been previously cloned (H. M. Champion, P. M. Bennett, D. A. Lewis, and D. S. Reeves, J. Antimicrob. Chemother. 22:587-596, 1988) was determined. High-pressure liquid chromatographic analysis of extracts prepared from Escherichia coli carrying the chromosomal aac(6')-Ic gene on a plasmid confirmed the presence of 6'-N-acetyltransferase activity in this strain, which was suggested by the aminoglycoside resistance profile. DNA sequence analysis of the cloned 2,057-bp PstI fragment revealed several regions of homology to previously characterized sequences from GenBank, including the rpoD and tRNA-2 genes of E. coli. Subcloning experiments confirmed the coding sequence of the aac(6')-Ic gene to be at positions 1554 to 1992. The predicted amino acid sequence of the AAC(6')-Ic protein suggested that it was the third member of a family of AAC(6') proteins which included a coding region identified between the aadB and aadA genes of Tn4000 and an AAC(6') protein encoded by pUO490, which was isolated from Enterobacter cloacae. Primer extension analysis suggested that the -35 region of the aac(6')-Ic promoter overlapped a large palindromic sequence which may be involved in the regulation of the aac(6')-Ic gene. Hybridization experiments utilizing a restriction fragment from the aac(6')-Ic gene showed that all S. marcescens organisms carried this gene whether or not the AAC(6')-I resistance profile was expressed. Organisms other than Serratia spp. did not hybridize to this probe.

Base Sequence↗
PubMed1994

Cloning and sequence analysis of the gene for a carbapenem-hydrolyzing class A beta-lactamase, Sme-1, from Serratia marcescens S6.

Serratia marcescens S6 produces a pI 9.7 carbapenem-hydrolyzing beta-lactamase that is probably encoded by the chromosome (Y. Yang, P. Wu, and D. M. Livermore, Antimicrob. Agents Chemother. 34:755-758, 1990). A total of 11.3 kb of genomic DNA from this strain was cloned into plasmid pACYC184 in Escherichia coli. After further subclonings, the carbapenem-hydrolyzing beta-lactamase gene (blaSme-1) was sequenced (EMBL accession number Z28968). The gene corresponded to an 882-bp open reading frame which encoded a 294-amino-acid polypeptide. This open reading frame was preceded by a -10 and a -35 region consistent with a putative promoter sequence of members of the family Enterobacteriaceae. This promoter was active in E. coli and S. marcescens, as demonstrated by primer extension analysis. N-terminal sequencing showed that the Sme-1 enzyme had a 27-amino-acid leader peptide and enabled calculation of the molecular mass of the mature protein (29.3 kDa). Sequence alignment revealed that Sme-1 is a class A serine beta-lactamase and not a class B metalloenzyme. The earlier view that the enzyme was zinc dependent was discounted. Among class A beta-lactamases, Sme-1 had the greatest amino acid identity (70%) with the pI 6.9 carbapenem-hydrolyzing beta-lactamase, NMC-A, from Enterobacter cloacae NOR-1. Comparison of these two protein sequences suggested a role for specific residues in carbapenem hydrolysis. The relatedness of Sme-1 to other class A beta-lactamases such as the TEM and SHV types was remote. This work details the sequence of the second carbapenem-hydrolyzing class A beta-lactamase from an enterobacterial species and the first in the genus Serratia.

Amino Acid Sequence↗
PubMed1974

Relation of cell wall lipid content of Serratia marcescens to resistance to antimicrobial agents.

Serratia marcescens strains were divided into three groups on the basis of antimicrobial sensitivity and pigment production. Group I, nonpigmented, was resistant to most antibiotics. Group II, nonpigmented, was susceptible to many antimicrobial agents, as was group III which was pigmented. Representative organisms of each group were examined for all lipid content. There were no significant differences in total lipid, phospholipid, or fatty acid esters among the three groups. Differences in susceptibility to antibiotics in Serratia do not seem to be explained on the basis of wall lipid content.

Anti-Bacterial Agents↗
PubMed1975

Antibiotic resistance patterns of clinical isolates of Serratia marcescens.

Antimicrobial susceptibility patterns of 102 clinical isolates of Serratia marcescens from three medical centers were studied by using disk sensitivity and agar dilution methods. The least resistance was demonstrated against gentamicin, nalidixic acid, chloramphenicol, and sulfisoxazole, all of which inhibited more than 80% of the strains. Cephalothin was completely ineffective, and more than 90% of strains were resistant to ampicillin and tetracycline. As demonstrated by the agar dilution method, the minimal inhibitory concentration of nalidixic acid, gentamicin, tobramycin, and chloramphenicol for most strains fell within therapeutically attainable concentrations. The prevalence of resistance to ampicillin, cephalothin, and tetracycline was nearly the same at all three medical centers, whereas there appeared to be patterns characteristic for each center with regard to the other drugs used. Eleven of the isolates produced pigment and exhibited patterns similar but not identical to those of the nonpigmented strains, all 11 being resistant to between three and six drugs. Half of the strains were resistant to five or more antibiotics, indicating that some Serratia exhibit resistance to an unusually broad range of therapeutic agents.

Anti-Bacterial Agents↗
PubMed1981

Prolonged survival of Serratia marcescens in chlorhexidine.

During an outbreak of Serratia marcescens infections at our hospital, we discovered widespread contamination of the 2% chlorhexidine hand-washing solution by S. marcescens. Examination by electron microscopy of the sides of bottles in which this solution was stored revealed that microorganisms were embedded in a fibrous matrix. Bacteria, free in the liquid, were morphologically abnormal, showing cell wall disruption or cytoplasmic changes. Furthermore, bacteria adherent to the walls of the storage jugs and embedded in this fibrous matrix also had morphologically abnormal cytoplasm. Despite these changes, viable S. marcescens organisms were recovered from the fluid during a storage period of 27 months. The concentration of chlorhexidine required to inhibit these strains of Serratia was 1,024 microgram/ml; however, the organism could survive in concentrations of up to 20,000 micrograms/ml. Additional studies are needed to define the mechanism(s) that allows such bacteria to contaminate and survive in disinfectants.

Cell Wall↗
PubMed1969

Klebsiella, Enterobacter, and Serratia: biochemical differentiation and susceptibility to ampicillin and three cephalosporin derivatives.

Three hundred twenty-nine strains of the tribe Klebsielleae were compared by several biochemical tests and by susceptibility to selected antibiotics. Biochemical tests included urease, amino acid decarboxylase, and hydrogen sulfide production; fermentation of lactose and dextrose; motility; and tests in the IMViC (indole, methyl red, Voges-Proskauer, citrate) series. The isolates were: Klebsiella species, 67.5%; Enterobacter species, 28%, and Serratia species, 4.5%. Minimal inhibitory concentrations of cephaloridine, cephalothin, and a new cephalosporin, cephalexin, and of ampicillin were determined by the agar dilution procedure. Cephalosporins at 20 mug/ml or less inhibited 90% of the Klebsiella strains but only 15% of the Enterobacter strains. Ampicillin inhibited 27% of Enterobacter strains and 17% of Klebsiella strains. Serratia isolates were insensitive to the cephalosporins and ampicillin. The results suggest that precise identification of this group to the generic level can be accomplished readily in the clinical laboratory and that such information is helpful in the preliminary selection of an antibiotic for treatment of clinical infections.

Ampicillin↗
PubMed1970

Differentiation of Serratia from Enterobacter on the basis of nucleoside phosphotransferase production.

Precoated cellulose thin-layer chromatograms were used to detect the production of guanosine 5'-phosphate from guanosine and p-nitrophenylphosphate by whole-cell preparations. One-hundred per cent of Serratia (163 strains) and 84% of E. liquefaciens (15 of 18 strains) produced the nucleotide. All other Enterobacter (23 strains), Klebsiella (10 strains), and E. coli (10 strains) were negative for the production of this nucleotide. The entire test procedure could be carried out in 4 hr. It is proposed that E. liquefaciens is more closely related to Serratia than Enterobacter and that reclassification of these organisms should be investigated.

Chromatography, Thin Layer↗
PubMed2005

Characterization of the dapA-nlpB genetic locus involved in regulation of swarming motility, cell envelope architecture, hemolysin production, and cell attachment ability in Serratia marcescens.

Swarming migration of Serratia marcescens requires both flagellar motility and cellular differentiation and is a population-density-dependent behavior. While the flhDC and quorum-sensing systems have been characterized as important factors regulating S. marcescens swarming, the underlying molecular mechanisms are currently far from being understood. Serratia swarming is thermoregulated and is characterized by continuous surface migration on rich swarming agar surfaces at 30 degrees C but not at 37 degrees C. To further elucidate the mechanisms, identification of specific and conserved regulators that govern the initiation of swarming is essential. We performed transposon mutagenesis to screen for S. marcescens strain CH-1 mutants that swarmed at 37 degrees C. Analysis of a "precocious-swarming" mutant revealed that the defect in a conserved dapA(Sm)-nlpB(Sm) genetic locus which is closely related to the synthesis of bacterial cell wall peptidoglycan is responsible for the aberrant swarming phenotype. Further complementation and gene knockout studies showed that nlpB(Sm), which encodes a membrane lipoprotein, NlpB(Sm), but not dapA(Sm), is specifically involved in swarming regulation. On the other hand, dapA(Sm) but not nlpB(Sm) is responsible for the determination of cell envelope architecture, regulation of hemolysin production, and cellular attachment capability. While the nlpB(Sm) mutant showed similar cytotoxicity to its parent strain, the dapA(Sm) mutant significantly increased in cytotoxicity. We present evidence that DapA(Sm) is involved in the determination of cell-envelope-associated phenotypes and that NlpB(Sm) is involved in the regulation of swarming motility.

Bacterial Adhesion↗
PubMed1974

Isolation and composition of oligosaccharide cores from endotoxins of two Serratia marcescens strains.

The oligosaccharide cores isolated from the acetic acid hydrolysates of endotoxins from Serratia marcescens 08 and Serratia marcescens Bizio were analyzed for their sugar composition. The intact oligosaccharide core from S. marcescens 08 consisted of 2-keto-3-deoxyoctonate, d-glycero-d-mannoheptose, l-glycero-d-mannoheptose, d-glucose, d-galactose, and d-glucosamine in a molar ratio of 2:1:5:3:1:3 and that from S. marcescens Bizio consisted of the same sugar components in a molar ratio of 2:1:5:5:1:2. This result indicates that endotoxins from S. marcescens genus may contain more than one structural type of oligosaccharide core. Both oligosaccharide cores also differ in their chemical compositions from cores of other Enterobacteriaceae.

Acetates↗
PubMed1986

Specific excretion of Serratia marcescens protease through the outer membrane of Escherichia coli.

A DNA fragment of Serratia marcescens directing an extracellular serine protease (Mr, 41,000) was cloned in Escherichia coli. The cloned fragment caused specific excretion of the protease into the extracellular medium through the outer membrane of E. coli host cells in parallel with their growth. No excretion of the periplasmic enzymes of host cells occurred. The cloned fragment contained a single open reading frame of 3,135 base pairs coding a protein of 1,045 amino acids (Mr 112,000). Comparison of the 5' nucleotide sequence with the N-terminal amino acid sequence of the protease indicated the presence of a typical signal sequence. The C-terminal amino acid of the enzyme was found at position 408, as deduced from the nucleotide sequence. Artificial frameshift mutations introduced into the coding sequence for the assumed distal polypeptide after the C terminus of the protease caused complete loss of the enzyme production. It was concluded that the Serratia serine protease is produced as a 112-kilodalton proenzyme and that its N-terminal signal peptide and a large C-terminal part are processed to cause excretion of the mature protease through the outer membrane of E. coli cells.

Amino Acid Sequence↗
PubMed1988

Molecular characterization of the hemolysin determinant of Serratia marcescens.

The nucleotide sequence of a 7.3-kilobase-pair fragment of DNA encoding a hemolytic activity from Serratia marcescens was determined. Two large open reading frames were identified, designated shlA (Serratia hemolysin) and shlB, capable of encoding polypeptides of 165, 056 and 61,897 molecular weight, respectively. Both reading frames were expressed in vivo. The shlB gene product was localized to the outer membrane of Escherichia coli cells harboring the S. marcescens hemolysin determinant. Consistent with this location, a signallike sequence was identified at the N terminus of the polypeptide predicted from the nucleotide sequence of the shlB gene. Hyperexpression of the shlB locus permitted the identification of two shlB-encoded polypeptides of 65,000 and 62,000 molecular weight, respectively. Determination of the N-terminal amino acid sequence of the purified 62,000-molecular-weight protein confirmed that it was the mature form of the ShlB protein initially synthesized as a precursor (65,000-molecular-weight protein). By using polyclonal antisera raised against the purified proteins, ShlA and ShlB were identified in the outer membrane of S. marcescens. The shlA gene product was shown to interact with erythrocyte membranes, confirming it as the hemolysin proper. Both hemolysis and the interaction of ShlA with erythrocyte membranes did, however, require the ShlB function. Progressive deletion of the C terminus of the ShlA protein gradually reduced hemolytic activity until 37% of the amino acids had been removed. Elimination of 54% of the amino acids produced a nonhemolytic protein which, however, was still capable of associating with erythrocyte membranes.

Amino Acid Sequence↗
PubMed1995

Relationships between rfb gene clusters required for biosynthesis of identical D-galactose-containing O antigens in Klebsiella pneumoniae serotype O1 and Serratia marcescens serotype O16.

The lipopolysaccharide O antigens of Klebsiella pneumoniae serotype O1 and Serratia marcescens serotype O16 both contain a repeating unit disaccharide of [-->3)-beta-D-Galf-(1-->3)-alpha-D-Galp-(1-->]; the resulting polymer is known as D-galactan I. In K. pneumoniae serotype O1, the genes responsible for the synthesis of D-galactan I are found in the rfb gene cluster (rfbKpO1). We report here the cloning and analysis of the rfb cluster from S. marcescens serotype O16 (rfbSmO16). This is the first rfb gene cluster examined for the genus Serratia. Synthesis of D-galactan I is an rfe-dependent process for both K. pneumoniae serotype O1 and S. marcescens serotype O16. Hybridization experiments with probes derived from each of the six rfbKpO1 genes indicate that the cloned rfbSmO16 cluster contains homologous genes arranged in the same order. However, the degree of homology at the nucleotide sequence level was sufficiently low that hybridization was detected only under low-stringency conditions. rfbABSmO16 genes were subcloned and shown to encode an ABC-2 (ATP-binding cassette) transporter which is functionally identical to the one encoded by the corresponding rfb genes from K. pneumoniae serotype O1. The amino acid sequences of the predicted RfbA and RfbB homologs showed identities of 75.7% (87.9% total similarity) and 78.0% (86.5% total similarity), respectively. The last gene of the rfbKpO1 cluster, rfbFKpO1, encodes a bifunctional galactosyltransferase which initiates the formation of D-galactan I. RfbFKpO1 and RfbFSmO16 are 57.6% identical (with 71.1% total similarity), and both show similarity with RfpB, the galactosyltransferase involved in the synthesis of Shigella dysenteriae type I O-polysaccharide. The G+C contents of the rfbAB genes from each organism are quite similar, and values are lower than those typical for the species. However, the G+C content of rfbFSmO16 (47.6%) was much higher than that of rfbFKpO1 (37.3%), despite the fact that the average for each species (52 to 60%) falls within the same range.

ATP-Binding Cassette Transporters↗
PubMed2000

Plasmid-located pathogenicity determinants of Serratia entomophila, the causal agent of amber disease of grass grub, show similarity to the insecticidal toxins of Photorhabdus luminescens.

Serratia entomophila and Serratia proteamaculans cause amber disease in the grass grub Costelytra zealandica (Coleoptera: Scarabaeidae), an important pasture pest in New Zealand. Larval disease symptoms include cessation of feeding, clearance of the gut, amber coloration, and eventual death. A 115-kb plasmid, pADAP, identified in S. entomophila is required for disease causation and, when introduced into Escherichia coli, enables that organism to cause amber disease. A 23-kb fragment of pADAP that conferred disease-causing ability on E. coli and a pADAP-cured strain of S. entomophila was isolated. Using insertion mutagenesis, the pathogenicity determinants were mapped to a 17-kb region of the clone. Sequence analysis of the 17-kb region showed that the predicted products of three of the open reading frames (sepA, sepB, and sepC) showed significant sequence similarity to components of the insecticidal toxin produced by the bacterium Photorhabdus luminescens. Transposon insertions in sepA, sepB, or sepC completely abolished both gut clearance and cessation of feeding on the 23-kb clone; when recombined back into pADAP, they abolished gut clearance but not cessation of feeding. These results suggest that SepA, SepB, and SepC together are sufficient for amber disease causation by S. entomophila and that another locus also able to exert a cessation-of-feeding effect is encoded elsewhere on pADAP.

Amino Acid Sequence↗
PubMed2003

Uptake of N,N'-diacetylchitobiose [(GlcNAc)2] via the phosphotransferase system is essential for chitinase production by Serratia marcescens 2170.

The chiR gene of Serratia marcescens 2170, encoding a LysR-type transcriptional activator, was identified previously as an essential factor for expression of chitinases and a chitin-binding protein, CBP21. To identify other genes that are essential for chitinase production, transposon mutagenesis with mini-Tn5Km1 was carried out, and 25 mutants that were unable to produce chitinases and CBP21 were obtained. Analysis of the mutated gene of one of the mutants, N22, revealed the presence of a pts operon in this bacterium, and a mutation was found in ptsI in the operon. In addition to its inability to produce chitinase, N22 did not grow well on N-acetyl-D-glucosamine (GlcNAc), (GlcNAc)(2), and some other carbon sources, most of which were phosphotransferase system (PTS) sugars. Thus, the inability to produce chitinase was assumed to be caused by the defect in uptake of (GlcNAc)(2) via the PTS, considering that (GlcNAc)(2) is the minimal substrate for chitinase induction and the major product of chitin hydrolysis by chitinases of this bacterium. To confirm this assumption, the chb operon, encoding the (GlcNAc)(2)-specific enzyme II permease, was cloned by reference to its Escherichia coli counterpart, and the Serratia chb operon was shown to comprise chbB, chbC, bglA, chbR, and chbG. Disruption of chbC drastically reduced production of chitinases and CBP21 and impaired growth on colloidal chitin. These results indicate that uptake of (GlcNAc)(2) is mediated by the PTS and that the (GlcNAc)(2)-specific enzyme II permease constitutes its major pathway. Since (GlcNAc)(2) uptake is essential for induction of chitinases and CBP21 production, (GlcNAc)(2) appears to be the key molecule in recognition and utilization of chitin by S. marcescens.

Chitin↗
PubMed2004

The global regulator genes from biocontrol strain Serratia plymuthica IC1270: cloning, sequencing, and functional studies.

The biocontrol activity of various fluorescent pseudomonads towards plant-pathogenic fungi is dependent upon the GacA/GacS-type two-component system of global regulators and the RpoS transcription sigma factor. In particular, these components are required for the production of antifungal antibiotics and exoenzymes. To investigate the effects of these global regulators on the expression of biocontrol factors by plant-associated bacteria other than Pseudomonas spp., gacA/gacS and rpoS homologues were cloned from biocontrol strain IC1270 of Serratia plymuthica, which produces a set of antifungal compounds, including chitinolytic enzymes and the antibiotic pyrrolnitrin. The nucleotide and deduced protein sequence alignments of the cloned gacA/gacS-like genes-tentatively designated grrA (global response regulation activator) and grrS (global response regulation sensor) and of the cloned rpoS gene revealed 64 to 93% identity with matching genes and proteins of the enteric bacteria Escherichia coli, Pectobacterium carotovora subsp. carotovora, and Serratia marcescens. grrA, grrS, and rpoS gene replacement mutants of strain IC1270 were deficient in the production of pyrrolnitrin, an exoprotease, and N-acylhomoserine lactone quorum-sensing signal molecules. However, neither mutant appeared to differ from the parental strain in the production of siderophores, and only grrA and grrS mutants were deficient in the production of a 58-kDa endochitinase, representing the involvement of other sigma factors in the regulation of strain IC1270's chitinolytic activity. Compared to the parental strain, the grrA, grrS, and rpoS mutants were markedly less capable of suppressing Rhizoctonia solani and Pythium aphanidermatum under greenhouse conditions, indicating the dependence of strain IC1270's biocontrol property on the GrrA/GrrS and RpoS global regulators.

Antifungal Agents↗