Antibiotic-Induced, Increased Conjugative Transfer Is Common to Diverse Naturally Occurring ESBL Plasmids in Escherichia coli

ABSTRACT We characterized the regions involved in replication and mobilization of the 40-kb plasmid pNZ4000, encoding exopolysaccharide (EPS) production in Lactococcus lactis NIZO B40. The plasmid contains four highly conserved replication regions with homologous rep genes (repB1, repB2,repB3, and repB4) that belong to the lactococcal theta replicon family. Subcloning of each replicon individually showed that all are functional and compatible in L. lactis. Plasmid pNZ4000 and genetically labeled derivatives could be transferred to different L. lactis strains by conjugation, and pNZ4000 was shown to be a mobilization plasmid. Two regions involved in mobilization were identified near two of the replicons; both included an oriT sequence rich in inverted repeats. Conjugative mobilization of the nonmobilizable plasmid pNZ124 was promoted by either one of these oriT sequences, demonstrating their functionality. One oriT sequence was followed by a mobA gene, coding for atrans-acting protein, which increased the frequency of conjugative transfer 100-fold. The predicted MobA protein and theoriT sequences show protein and nucleotide similarity, respectively, with the relaxase and with the inverted repeat andnic site of the oriT from the Escherichia coli plasmid R64. The presence on pNZ4000 of four functional replicons, two oriT sequences, and several insertion sequence-like elements strongly suggests that this EPS plasmid is a naturally occurring cointegrate.

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Insect-Mediated Dispersal of the Rhizobacterium Pseudomonas chlororaphis

Phytopathology ◽

10.1094/phyto.1998.88.12.1248 ◽

1998 ◽

Vol 88 (12) ◽

pp. 1248-1254 ◽

Cited By ~ 10

Author(s):

William E. Snyder ◽

David W. Tonkyn ◽

Daniel A. Kluepfel

Keyword(s):

Escherichia Coli ◽

Adult Stage ◽

Genetically Modified ◽

Insect Pest ◽

Corn Rootworm ◽

Transmission Route ◽

Pseudomonas Chlororaphis ◽

Naturally Occurring ◽

Southern Corn Rootworm ◽

Corn Plants

The southern corn rootworm, Diabrotica undecimpunctata subsp. howardi, a common and mobile insect pest, was shown to transmit the rhizobacte-rium Pseudomonas chlororaphis strain L11 between corn plants. Strain L11 has been genetically modified to contain the lacZY genes from Escherichia coli. It can reach high densities on roots and invade the roots and move into the foliage. D. undecimpunctata subsp. howardi became infested with L11 as larvae while feeding on roots of seed-inoculated corn and retained the bacteria through pupation, molting to the adult stage, and emergence from the soil. Bacterial densities on or in the insects increased 100-fold after they fed again as adults on L11-infested foliage. Adults retained the bacteria for at least 2 weeks after last exposure and could transmit L11 to new plants. The likelihood of transmission decreased with time since last exposure to L11, but increased with time spent on the new plants. This research demonstrates that rhizobacteria can escape the rhizosphere by moving in or onto foliage, where they can then be acquired and transmitted by insects. This transmission route may be common among naturally occurring rhizobacteria and facilitate the dispersal of both beneficial and harmful soilborne microorganisms.

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The Structural Gene for Microcin H47 Encodes a Peptide Precursor with Antibiotic Activity

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.43.9.2176 ◽

1999 ◽

Vol 43 (9) ◽

pp. 2176-2182 ◽

Cited By ~ 28

Author(s):

Eliana Rodríguez ◽

Carina Gaggero ◽

Magela Laviña

Keyword(s):

Escherichia Coli ◽

Gene Fusion ◽

Genetic System ◽

Antibiotic Activity ◽

Peptide Antibiotic ◽

Bifunctional Protein ◽

Naturally Occurring ◽

Hydrophobic Peptide ◽

Peptide Precursor ◽

Highly Hydrophobic

ABSTRACT Microcin H47 is a bactericidal antibiotic produced by a naturally occurring Escherichia coli strain isolated in Uruguay. The microcin genetic system is located in the chromosome and extends over a 10-kb DNA segment containing the genes required for microcin synthesis, secretion, and immunity. The smallest microcin synthesis gene,mchB, was sequenced and shown to encode a highly hydrophobic peptide. An mchB-phoA gene fusion, which directed the synthesis of a hybrid bifunctional protein with both PhoA and microcin H47-like activities, was isolated. The results presented herein lead us to propose that microcin H47 is indeed a ribosomally synthesized peptide antibiotic and that its peptide precursor already has antibiotic activity of the same specificity as that of mature microcin.

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Survival of Bacteria in “Soul Foods” at 10-Centigrade

Journal of Food Protection ◽

10.4315/0362-028x-44.4.271 ◽

1981 ◽

Vol 44 (4) ◽

pp. 271-274

Author(s):

ADELLE W. STEWART

Keyword(s):

Escherichia Coli ◽

Staphylococcus Aureus ◽

Salmonella Typhimurium ◽

Food Samples ◽

Viable Count ◽

Inoculum Size ◽

Farm Families ◽

Farm Family ◽

Collard Greens ◽

Naturally Occurring

The fate of naturally occurring and added bacterial pathogens was determined in “soul foods” purchased at local supermarkets and farm families while the foods were stored under conditions simulating those used for retail distribution, home storage, and preparation before use. Viable count determinations for 10 samples at the end of a 5-day period at 10 C showed considerable decreases in comparison to the inoculum size, indicating that growth was not promoted. Escherichia coli survived in all the food samples but the populations decreased by 1 to 9 log cycles/g of food. Salmonella typhimurium survived in 59% of the food samples. Except for farm family collard greens and sausage (encased), Staphylococcus aureus remained viable in all of the foods tested an d was the only survivor in cracklings (cooked) obtained from both sources. Clostridium perfringens was detected in farm family sweet peas and 23% of the pig offal samples.

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