Antimicrobial Activity of Aqueous Herbal Extracts

Abstract: Some plants contain various compounds, which can influence microbial growth, reproduction or basic cell functions. Phenols, polyphenols, micronutrients, essential oils and other compounds belong to them. These compounds are primarily present in various herbs. Extracts from these plants could be used as natural food preservatives, which could inhibit growth of undesirable microorganisms. In this work, antimicrobial activity of aqueous extracts of Thymus vulgaris, Lavandula angustifolia, Melissa officinalis, Ocimum basilicum, Allium schoenoprasum and Petroselinum crispum was tested on five gram negative bacteriaEscherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Hafnia alvei and Raoultella terrigena, which were isolated from dairy products except Escherichia coli (CCM 7929). Antimicrobial activity was tested by disc diffusion method. It was found out the less effective extracts were from thyme and lavender. Basil, chive and parsley extracts showed higher potential to inhibit bacterial growth

Study of antioxidant and antimicrobial properties of grapevine seeds, grape and rosehip pressing

In our experiment, we studied the antimicrobial and antioxidative effect of phytogenic additives. Three additives (grapevine seeds, grape and rosehip pressings) were selected to be monitored. The extracts about concentrations of 1:3 and 1:5 were prepared from them. The monitoring of antimicrobial properties was focused on the pathogenic bacteria Clostridium perfringens and Escherichia coli causing a serious disease in avian species. The bacteria were prepared in the dilutions of 102, 104 and 106. The antimicrobial effect was observed in the inhibition zones. The antioxidant activity was determined using DPPH method within the antioxidant analysis. Furthermore, the content of flavanols, hydroxycinnamic acids and the total content of polyphenolic compounds was also determined. In the monitoring of the antimicrobial effect of grapevine seeds, grape and rosehip pressings at E. coli, a reduced growth of KTJ (colony forming units) was observed in the disk area during the dilution of 106 and 104. Reduced growth of C. perfringens at a dilution of 106 was noticed using the extracts of grapevine seeds and grape pressings. Low reduced growth of C. perfringens at a dilution of 106 was found out using rosehip pressings. In a dilution of 102 and 104 in C. perfringens and 102 in E. Coli, a very low increase of KTJ was observed therefore the zones of inhibition were not possible to measure. In all monitored additives, the antimicrobial effect was proved. The additives reduced the growth of pathogenic E. coli and C. perfringens. Within the antioxidant analysis, the highest antioxidant activity was found out in grapevine seeds (7.021 g.L-1 GAE), which also contained the highest content of flavanols (3000 times higher than the rosehip pressings and 300 times higher than grapevine seeds pressings), hydroxycinnamic acids (1000 times higher than in grape pressings and 7600 times higher than in rosehip pressings) and the total content of polyphenolic compounds (580 times higher than grape pressings and 2000 times higher than the rosehip pressings) of the monitored additives

Assignment of sigma factors of RNA polymerase to promoters in Corynebacterium glutamicum

Dostalova H, Holatko J, Busche T, et al. Assignment of sigma factors of RNA polymerase to promoters in Corynebacterium glutamicum. AMB EXPRESS. 2017;7(1): 133.Corynebacterium glutamicum is an important industrial producer of various amino acids and other metabolites. The C. glutamicum genome encodes seven sigma subunits (factors) of RNA polymerase: the primary sigma factor SigA (sA), the primary-like sigma(B) and five alternative sigma factors (sigma(C), sigma(D), sigma(E), sigma(H) and sigma(M)). We have developed in vitro and in vivo methods to assign particular sigma factors to individual promoters of different classes. In vitro transcription assays and measurements of promoter activity using the overexpression of a single sigma factor gene and the transcriptional fusion of the promoter to the gfpuv reporter gene enabled us to reliably define the sigma factor dependency of promoters. To document the strengths of these methods, we tested examples of respective promoters for each C. glutamicum sigma factor. Promoters of the rshA (anti-sigma for sH) and trxB1 (thioredoxin) genes were found to be sigma(H)-dependent, whereas the promoter of the sigB gene (sigma factor sigma(B)) was sigma(E)-and sigma(H)-dependent. It was confirmed that the promoter of the cg2556 gene (iron-regulated membrane protein) is sigma(C)-dependent as suggested recently by other authors. The promoter of cmt1 (trehalose corynemycolyl transferase) was found to be clearly sigma(D)-dependent. No sigma(M)-dependent promoter was identified. The typical housekeeping promoter P2sigA (sigma factor sigma(A)) was proven to be sigma(A)-dependent but also recognized by sigma(B). Similarly, the promoter of fba (fructose-1,6-bisphosphate aldolase) was confirmed to be sigma(B)-dependent but also functional with sigma(A). The study provided demonstrations of the broad applicability of the developed methods and produced original data on the analyzed promoters

Overlapping SigH and SigE sigma factor regulons in Corynebacterium glutamicum

Busche T, Dostalova H, Rucka L, et al. Overlapping SigH and SigE sigma factor regulons in Corynebacterium glutamicum. Frontiers in Microbiology . 2022;13: 1059649.The sigma H (sigmaEta) and sigma E (sigmaE) subunits of Corynebacterium glutamicum RNA polymerase belong to Group 4 of sigma factors, also called extracytoplasmic function (ECF) sigma factors. Genes of the C. glutamicum sigmaEta regulon that are involved in heat and oxidative stress response have already been defined, whereas the genes of the sigmaE regulon, which is involved in cell surface stress response, have not been explored until now. Using the C. glutamicum RES167 strain and its derivative C. glutamicum DeltacseE with a deletion in the anti-sigmaEpsilon gene, differential gene expression was analyzed by RNA sequencing. We found 296 upregulated and 398 downregulated genes in C. glutamicum DeltacseE compared to C. glutamicum RES167. To confirm the functional link between sigmaEpsilon and the corresponding promoters, we tested selected promoters using the in vivo two-plasmid system with gfpuv as a reporter gene and by in vitro transcription. Analyses with RNAP+sigmaEta and RNAP+sigmaEpsilon, which were previously shown to recognize similar promoters, proved that the sigmaEta and sigmaE regulons significantly overlap. The sigmaE-controlled genes were found to be involved for example in protein quality control (dnaK, dnaJ2, clpB, and clpC), the regulation of Clp proteases (clgR), and membrane integrity maintenance. The single-promoter analyses with sigmaEta and sigmaEpsilon revealed that there are two groups of promoters: those which are exclusively sigmaEta-specific, and the other group of promoters, which are sigmaEta/sigmaE-dependent. No exclusively sigmaE-dependent promoter was detected. We defined the consensus sequences of exclusively sigmaEta-regulated promotors to be -35 GGAAt and-10 GTT and sigmaEta/sigmaE-regulated promoters to be -35 GGAAC and-10 cGTT. Fifteen genes were found to belong to the sigmaEta/sigmaEpsilon regulon. Homology modeling showed that there is a specific interaction between Met170 in sigmaEta and the nucleotides -31 and-30 within the non-coding strand (AT or CT) of the sigmaEta-dependent promoters. In sigmaE, Arg185 was found to interact with the nucleotides GA at the same positions in the sigmaE-dependent promoters. Copyright © 2023 Busche, Dostalova, Rucka, Holatko, Barvik, Stepanek, Patek and Kalinowski

Sigma regulatory network in Rhodococcus erythropolis CCM2595

Stepanek V, Dostalova H, Busche T, et al. Sigma regulatory network in Rhodococcus erythropolis CCM2595. FEMS Microbiology Letters. 2022;369(1): fnac014.The aim of this investigation was to discover the promoters that drive expression of the sig genes encoding sigma factors of RNA polymerase in Rhodococcus erythropolis CCM2595 and classify these promoters according to the sigma factors which control their activity. To analyze the regulation of major sigma factors, which control large regulons that also contain genes expressed under exponential growth and non-stressed conditions, we used the R. erythropolis CCM2595 culture, which grew rapidly in minimal medium. The transcriptional start sites (TSSs) of the genes sigA, sigB, sigD, sigE, sigG, sigH, sigJ, and sigK were detected by primary 5'-end-specific RNA sequencing. The promoters localized upstream of the detected TSSs were defined by their -35 and -10 elements, which were identical or closely similar to these sequences in the related species Corynebacterium glutamicum and Mycobacterium tuberculosis. Regulation of the promoter activities by different sigma factors was demonstrated by two independent techniques (in vivo and in vitro). All analyzed sig genes encoding the sigma factors with extracytoplasmic function (ECF) were found to be also driven from additional housekeeping promoters. Based on the classification of the sig gene promoters, a model of the basic sigma transcriptional regulatory network in R. erythropolis was designed. © The Author(s) 2022. Published by Oxford University Press on behalf of FEMS

Effect of chamomile supplements to feeding doses on antimicrobial parameters in poultry

Due to a ban of use of antibiotic growth promoters in the poultry industry it is necessary to look for alternative solutions. The use of some herbs showing antimicrobial effects can be one of such alternatives. In this experiment, effects of three different concentrations of chamomile (Matricaria chamomilla) extract, (0.3%; 0.6% and 1.2%) in feeding doses on the microbial population in the gastrointestinal tract of growing broiler chickens were studied. The main attention was paid to the population of Clostridium perfringens and to numbers of coliform microbes. Clostridia were cultivated under anaerobic conditions at 46 &deg;C on the Tryptone Sulfite Neomycin (TSN) agar for a period of 24 hours. Coliform microbes were grown on the violet red bile lactose (VRBL) agar at 37 &deg;C for a period of 24 hours. The experiment lasted 39 days and involved 80 chicks that were slaughtered in the course of their growth period at the age of 18, 25, 32 and 39 days; there were 5 chicks in each group. The obtained results indicated that increasing doses of chamomile in the feeding ration decreased numbers of coliform microbes in the digestive tract of chicks and also reduced the population of C. perfingens.<br /