Characterization of a bacteriocinogenic plasmid in Clostridium perfringens CW55

Virulence Plasmids of the Pathogenic Clostridia

The clostridia cause a spectrum of diseases in humans and animals ranging from life-threatening tetanus and botulism, uterine infections, histotoxic infections and enteric diseases, including antibiotic-associated diarrhea, and food poisoning. The symptoms of all these diseases are the result of potent protein toxins produced by these organisms. These toxins are diverse, ranging from a multitude of pore-forming toxins to phospholipases, metalloproteases, ADP-ribosyltransferases and large glycosyltransferases. The location of the toxin genes is the unifying theme of this review because with one or two exceptions they are all located on plasmids or on bacteriophage that replicate using a plasmid-like intermediate. Some of these plasmids are distantly related whilst others share little or no similarity. Many of these toxin plasmids have been shown to be conjugative. The mobile nature of these toxin genes gives a ready explanation of how clostridial toxin genes have been so widely disseminated both within the clostridial genera as well as in the wider bacterial community.

Conjugal Transfer of Plasmid-Encoded Determinants for Bacteriocin Production and Immunity in Lactobacillus acidophilus 88

Lactobacillus acidophilus 88 produced a bacteriocin, designated lactacin F, that demonstrated inhibitory activity toward L. acidophilus 6032, L. lactis 970, L. helveticus 87, L. bulgaricus 1489, L. leichmanii 4797, L. fermentum 1750, and Streptococcus faecalis 19433. Production of lactacin F was pH dependent and could be maximized in MRS broth cultures maintained at pH 7.0. Lactacin F was heat stable and sensitive to ficin, proteinase K, trypsin, and Bacillus subtilis protease. L. acidophilus 88 harbored plasmids of 4 and 27 megadaltons. Variants of L. acidophilus 88 which were deficient in lactacin F production (Laf) and lactacin F immunity (Laf) retained the two resident plasmids. A Laf Laf derivative, L. acidophilus 89, was used as a recipient in agar surface mating experiments with L. acidophilus 88 (Laf Laf). Two types of Laf Laf transconjugants were recovered. One type (T-E) had acquired two plasmids of 68 (pPM68) and 52 (pPM52) megadaltons that were not detected in either the conjugal donor or the other type of Laf Laf transconjugants (T-89). Laf and Laf were unstable in the plasmid-bearing transconjugant. Plasmid analysis of Laf Laf variants revealed that pPM52 and pPM68 were cured with loss of Laf and Laf. Bacteriocin production and immunity phenotypes were genetically stable in Laf Laf transconjugants not harboring pPM52 and pPM68, suggesting chromosomal integration of the transferred determinants. The data demonstrated intragenic conjugation in L. acidophilus and provided direct evidence for involvement of transient plasmid determinants in Laf and Laf.

Human disease associated with Clostridium perfringens enterotoxin

Clostridium perfringens continues to be a common cause of food-borne disease. Characteristics of this organism that contribute to its ability to cause food-borne illness include the formation of heat-resistant spores that survive normal cooking/heating temperatures, a rapid growth rate in warm food, and the production of enterotoxin (CPE) in the human gut. Time and temperature abuse associated with food preparation contributes to the majority of outbreaks of C. perfringens food-borne disease. CPE-induced diarrhea has been reported in the absence of a defined food vehicle. These cases have been typically associated with the elderly and following a course of antibiotic therapy. The incidence of CPE-induced diarrhea may be expected to increase with the growing population of immunocompromised (disease-, treatment-, or age-induced) individuals. Clostridium perfringens has been implicated as a possible contributor to the development of SIDS in susceptible individuals. Specifically, it has been hypothesized that CPE acts as a triggering agent, initiating the events associated with the development of SIDS. Continued refinement of both immunoassays and molecular methods for toxin and gene detection, respectively, will facilitate their eventual availability as commercial kits, providing rapid and simplified methods for the detection of C. perfringens isolates that produce or have the capacity to produce CPE as well as other toxins associated with this organism.

Molecular genetics and pathogenesis of Clostridium perfringens

Clostridium perfringens is the causative agent of a number of human diseases, such as gas gangrene and food poisoning, and many diseases of animals. Recently significant advances have been made in the development of C. perfringens genetics. Studies on bacteriocin plasmids and conjugative R plasmids have led to the cloning and analysis of many C. perfringens genes and the construction of shuttle plasmids. The relationship of antibiotic resistance genes to similar genes from other bacteria has been elucidated. A detailed physical map of the C. perfringens chromosome has been prepared, and numerous genes have been located on that map. Reproducible transformation methods for the introduction of plasmids into C. perfringens have been developed, and several genes coding for the production of extracellular toxins and enzymes have been cloned. Now that it is possible to freely move genetic information back and forth between C. perfringens and Escherichia coli, it will be possible to apply modern molecular methods to studies on the pathogenesis of C. perfringens infections.

Characterization of two bacteriocins produced by Clostridium perfringens

Two types of bacteriocins were shown to be produced in succession by a strain of Clostridium perfringens SN-17. They were separated by diethylaminoethyl cellulose (DEAE) column chromatography at pH 8.5 with a linear concentration gradient of NaCl. One type of bacteriocin (named SN-a) was eluted at 0.07 M and the other type (named SN-b) was at 0.12 M. Each of these was partially purified in a series of column chromatographies: DEAE, Sephadex G-200 (or Bio Gel P-150), and hydroxyapatite. Specific activities of SN-a and SN-b after the last chromatography were at most 30- to 50-fold that of culture filtrate of the organisms. Chromatographed SN-a migrated as a single zone in polyacrylamide gel electrophoresis (PAGE) and the zone showed high biological activity. On the other hand, PAGE pattern of SN-b revealed the presence of a few contamination materials. The activity of SN-b after the last chromatography was hardly recovered from the gel but inactivated SN-b was identified in the gel by examining bacteriocin activity of the DEAE fractions recovered from the gel. The molecular weight of the SN-a and SN-b was determined to be about 70,000 and 100,000, respectively, by molecular sieve chromatography. These bacteriocins were very sensitive to protease but insensitive to DNase and RNase. Bacteriocins were both completely inactivated at 55 C and they were more stable in alkaline pH than in acidic pH. SN-a and SN-b were adsorbed in different ways on the surface of the producer and insensitive strains. Several differences and similarities between these 2 bacteriocins are discussed with special reference to the relationship between them.

Extrachromosomal systems and gene transmission in anaerobic bacteria

Obligately anaerobic bacteria are important in terms of their role as medical pathogens as well as their degradative capacities in a variety of natural ecosystems. Two major anaerobic genera, Bacteroides and Clostridium, are examined in this review. Plasmid elements in both genera are reviewed within the context of conjugal transfer and drug resistance. Genetic systems that facilitate the study of these anaerobic bacteria have emerged during the past several years. In large part, these developments have been linked to work centered on extrachromosomal genetic systems in these organisms. Conjugal transfer of antibiotic resistance has been a central focus in this regard. Transposable genetic elements in the Bacteroides are discussed and the evolution and spread of resistance to lincosamide antibiotics are considered at the molecular level. Recombinant DNA systems that employ shuttle vectors which are mobilized by conjugative plasmids have been developed for use in Bacteroides and Clostridium. The application of transmission and recombinant DNA genetic systems to study these anaerobes is under way and is likely to lead to an increased understanding of this important group of procaryotes.

Characterization and purification of helveticin J and evidence for a chromosomally determined bacteriocin produced by Lactobacillus helveticus 481

Lactobacillus helveticus 481 produced an antimicrobial agent active against five closely related species. The sensitive indicators included L. helveticus 1846 and 1244, L. bulgaricus 1373 and 1489, and L. lactis 970. The antimicrobial compound was active at neutral pH under aerobic or anaerobic conditions, was sensitive to proteolytic enzymes and heat (30 min at 100 degrees C), and demonstrated a bactericidal mode of action against sensitive indicators. These data confirmed that antimicrobial activity of L. helveticus 481 was mediated by a bacteriocin, designated helveticin J. Production of helveticin J was maximized in an anaerobic fermentor held at a constant pH of 5.5. Ultrafiltration experiments on culture supernatants containing the bacteriocin revealed that helveticin J was present as an aggregate with a molecular weight in excess of 300,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of helveticin J purified through Sephadex chromatography resolved a 37,000-dalton protein band with bacteriocin activity. L. helveticus 481 was shown to harbor a single 8-megadalton plasmid (pMJ1008). Isolates cured of pMJ1008 were phenotypically identical to plasmid-bearing cells in fermentation patterns, helveticin J activity, and immunity spectra. The data provided evidence for a chromosomal location of helveticin J and host immunity determinants.

Role of DNase in recovery of plasmid DNA from Clostridium perfringens

Recovery of plasmid DNA from Clostridium perfringens 10543A and 3626B cleared lysates was significantly improved by the addition of 0.2% (vol/vol) diethylpyrocarbonate (DEP) before protoplast disruption in the cleared lysate protocol. Three previously undetected, large-molecular-mass plasmids (45.2, 51.9, and 68.2 megadaltons) were isolated from modified DEP-treated cleared lysates of C. perfringens 3626B. Two plasmids (9.4 and 30 megadaltons) were recovered from C. perfringens 10543A modified DEP-treated cleared lysates which previously required dye-buoyant density gradient centrifugation for visualization on agarose gels. Unsuccessful attempts to isolate plasmid DNA from Brij 58 cleared lysates of extracellular DNase-negative mutants of C. perfringens suggested the deleterious DNase activity was not extracellular. Cellular localization studies indicated that the cell wall-compartmentalized cell fraction contained 72.2% of the total DNase activity, whereas the extracellular and intracellular fractions demonstrated much less (26.8 and 1.0%, respectively). Cleared lysates prepared with DEP demonstrated much less DNase activity than cleared lysates prepared without DEP. The variable and irreproducible recovery of plasmid DNA from C. perfringens cleared lysates was attributed to cell wall-compartmentalized DNase.

Characterization of Lactobacillus sp. strain 100-37 from the murine gastrointestinal tract: ecology, plasmid content, and antagonistic activity toward Clostridium ramosum H1

A gram-positive, nonsporulating, microaerophilic rod that had two colonial variants was obtained during a study in which anaerobic bacteria were isolated from murine gastrointestinal tracts and screened for cryptic plasmids. The rod (both colonial variants) was identified as a Lactobacillus sp. (strain 100-37) by selective media, gas chromatography, and biochemical tests. In monoassociated, ex-germfree mice, the bacterium colonized the gastrointestinal tract and formed a thick, continuous layer on the keratinized squamous epithelium of the nonsecreting portion of the stomach. When lysate preparations of both colonial variants were electrophoresed in agarose gels, two bands which stained with ethidium bromide were detected with each lysate. When the DNA preparations were exposed to UV light, the lower ethidium bromide band gradually disappeared while the top band became either broader or more intense. The approximate size of the lower band was 2.2 megadaltons, as determined by comparison with plasmid molecular weight standards. In a search for phenotypes which could be encoded by the cryptic 2.2-megadalton plasmid, we detected an antagonistic activity toward an obligate anaerobe isolated from mouse feces, Clostridium ramosum H1. The antagonistic factor was precipitated with (NH4)2SO4 (70% saturation) from supernatant solutions of broth cultures of strain 100-37. The factor was not inducible with mitomycin C or UV light, but was stable in flowing steam for up to 50 min, and in buffers of pHs over a range of 1.6 to 6.8. It was nondialyzable and inactivated by trypsin and papain.(ABSTRACT TRUNCATED AT 250 WORDS)