Antimicrobial activity of experimental formulations of two structurally different nano-zinc oxide materials, plate-like Zinkicide SG4 and particulate Zinkicide SG6, was evaluated against Xanthomonas citri subsp. citri, the cause of citrus canker. In vitro assay demonstrated Zinkicide SG4 had a twofold lower minimum inhibitory concentration (MIC) against Escherichia coli and X. alfalfae subsp. citrumelonis (62.5 to 250 µg/ml) compared with copper sulfate (250 µg/ml), copper hydroxide (250 to 500 µg/ml), or cuprous oxide/zinc oxide (125 to 250 µg/ml). Zinkicide SG6 had a sevenfold to eightfold lower MIC against Escherichia coli and X. alfalfae subsp. citrumelonis (31 to 250 μg/ml). Leaves of sweet orange (Citrus sinensis) and fruit of ‘Ruby Red’ grapefruit (C. paradisi) were evaluated for citrus canker disease control. A greenhouse assay with foliage demonstrated that spray treatment with Zinkicide reduced citrus canker lesion development after injection-infiltration of X. citri subsp. citri into the leaf intercellular space. In field trials conducted in Southeast Florida in 2014 and 2015, Zinkicide SG4 and SG6 reduction of grapefruit canker incidence exceeded that of cuprous oxide and cuprous oxide/zinc oxide bactericides. Zinkicide formulations were also effective against the fungal diseases, citrus scab (Elsinoe fawcetti) and melanose (Diaporthe citri), on grapefruit. No sign of phytotoxicity to the fruit rind was observed during either season. Antimicrobial activity of Zinkicide for protection of leaves and fruit against X. citri subsp. citri was comparable or exceeded that for commercial copper and zinc oxide formulations which may be attributed to translaminar movement of Zinkicide.
Background: In prokaryotes, the ureases are multi-subunit, nickel-containing enzymes that catalyze the hydrolysis of urea to carbon dioxide and ammonia. The Brucella genomes contain two urease operons designated as ure1 and ure2. We investigated the role of the two Brucella suis urease operons on the infection, intracellular persistence, growth, and resistance to low-pH killing.
Peptide nucleic acids (PNAs) are single-stranded, synthetic nucleic acid analogues containing a pseudopeptide backbone in place of the phosphodiester sugar–phosphate. When PNAs are covalently linked to cell-penetrating peptides (CPPs) they readily penetrate the bacterial cell envelope, inhibit expression of targeted genes and cause growth inhibition both of Gram-positive and Gram-negative bacteria. However, the effectiveness of PNAs against Brucella, a facultative intracellular bacterial pathogen, was unknown. The susceptibility of a virulent Brucella suis strain to a variety of PNAs was assessed in pure culture as well as in murine macrophages. The studies showed that some of the PNAs targeted to Brucella genes involved in DNA (polA, dnaG, gyrA), RNA (rpoB), cell envelope (asd), fatty acid (kdtA, acpP) and protein (tsf) synthesis inhibit the growth of B. suis in culture and in macrophages after 24 h of treatment. PNA treatment inhibited Brucella growth by interfering with gene expression in a sequence-specific and dose-dependent manner at micromolar concentrations. The most effective PNA in broth culture was that targeting polA at ca. 12 μM. In contrast, in B. suis-infected macrophages, the most effective PNAs were those targeting asd and dnaG at 30 μM; both of these PNAs had little inhibitory effect on Brucella in broth culture. The polA PNA that inhibits wild-type B. suis also inhibits the growth of wild-type Brucella melitensis 16M and Brucella abortus 2308 in culture. This study reveals the potential usefulness of antisense PNA constructs as novel therapeutic agents against intracellular Brucella.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.