Impact of pectin esterification on the antimicrobial activity of nisin-loaded pectin particles.

The relationship between pectin structure and the antimicrobial activity of nisin-loaded pectin particles was examined. The antimicrobial activity of five different nisin-loaded pectin particles, i.e., nisin-loaded high methoxyl pectin, low methoxyl pectin, pectic acid, dodecyl pectin with 5.4 and 25% degree of substitution were tested in the pH range of 4.0-7.0 by agar-diffusion assay and agar plate count methods. It was found that the degree of esterification of carboxyl group of galacturonic acid in pectin molecule is important for the antimicrobial activity of nisin-loaded pectin particles. Nisin-loaded particles prepared using pectic acid or the pectin with low degree of esterification exhibit higher antimicrobial activity than nisin-loaded high methoxyl pectin particles. Pectins with free carboxyl groups or of low degree of esterification are the most suitable for particles preparation. Moreover, nisin-loaded pectin particles were active at close to neutral or neutral pH values. Therefore, they could be effectively applied for food preservation. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:245-251, 2017.

[Applicability of MALDI Mass Spectrometry for Diagnostics of Phase Variants in Bacterial Populations].

Efficiency of MALDI mass spectrometry for differentiation between phenotypic phase variants (in colony morphology and virulence/avirulence) was investigated.for saprotrophic and opportunistically pathogenic bacteria of five genera (Acinetobacter, Arthrobacter, Rhodococcus, Corynebacterium, and Escherichia). Analysis of MALDI spectra (on the SA and HCCA matrices) included: (1) determination of similarity of the protein spectra as a percentage of the common protein peaks to the total amount of proteins, which reflects the phylogenetic relationships of the objects and has been recommended for identification of closely related species; (2) comparison of intensities of the common peaks; and (3) the presence of specific peaks as determinative characteristics of the variants. Under the standard analytical conditions the similarity between the MALDI profiles was shown to increase in the row: genus-species-strain-variant. Assessment of intensities of the common peaks was most applicable for differentiation between phase variants, especially in the case of high similarity of their profiles. Phase variants (A. oxydans strain K14) with similar colony morphotypes (S, R, M, and S(m)) grown on different media (LB agar, TSA, and TGYg) exhibited differences in their protein profiles reflecting the differences in their physiological characteristics. This finding is in agreement with our previous results on screening of the R. opacus with similar colony morphology and different substrate specificity in decomposition of chlorinated phenols. Analysis of MALDI spectra is probably the only efficient method for detection of such variants.

Reconsideration of Arthrobacter ilicis (Mandel et al. 1961) Collins et al. 1982 as a plant-pathogenic species. Proposal to emend the authority and description of the species. Request for an opinion.

Strains now considered to represent the type strain of Arthrobacter ilicis, described as a pathogen of American holly, are not identical. The designated type strain does not represent this pathogen. However, one of the other strains sourced to the type strain of the pathogen does appear to be authentic, but is not a member of A. ilicis. It is proposed that A. ilicis is an unrelated species, not a pathogen of American holly. The nomenclature of A. ilicis can be rectified by emending the authority and by emending the species description to recognize this species as a novel species that is not a plant pathogen. The pathogen of American holly then becomes a novel pathovar, Curtobacterium flaccumfaciens pv. ilicis. The opinion of the Judicial Commission is sought.