108 research outputs found
Mutation in the pssZ Gene Negatively Impacts Exopolysaccharide Synthesis, Surface Properties, and Symbiosis of Rhizobium leguminosarum bv. trifolii with Clover
Rhizobium leguminosarum bv. trifolii is a soil bacterium capable of establishing a nitrogen-fixing symbiosis with clover plants (Trifolium spp.). This bacterium secretes large amounts of acidic exopolysaccharide (EPS), which plays an essential role in the symbiotic interaction with the host plant. This polymer is biosynthesized by a multi-enzymatic complex located in the bacterial inner membrane, whose components are encoded by a large chromosomal gene cluster, called Pss-I. In this study, we characterize R. leguminosarum bv. trifolii strain Rt297 that harbors a Tn5 transposon insertion located in the pssZ gene from the Pss-I region. This gene codes for a protein that shares high identity with bacterial serine/threonine protein phosphatases. We demonstrated that the pssZ mutation causes pleiotropic effects in rhizobial cells. Strain Rt297 exhibited several physiological and symbiotic defects, such as lack of EPS production, reduced growth kinetics and motility, altered cell-surface properties, and failure to infect the host plant. These data indicate that the protein encoded by the pssZ gene is indispensable for EPS synthesis, but also required for proper functioning of R. leguminosarum bv. trifolii cells.Polish National Science Centre grant no. DEC-2012/07/B/NZ1/0009
The effect of Galleria mellonella hemolymph polypeptides on Legionella gormanii
Among Legionella species, which are recognized to be pathogenic for humans, L. gormanii is the second prevalent causative agent of community-acquired pneumonia after L. pneumophila. Anti-L. gormanii activity of Galleria mellonella hemolymph extract and apolipophorin III (apoLp-III) was examined. The extract and apoLp-III at the concentration 0.025 mg/ml caused 75% and 10% decrease of the bacteria survival rate, respectively. The apoLp-III-induced changes of the bacteria cell surface were analyzed for the first time by atomic force microscopy. Our studies demonstrated the powerful anti-Legionella effects of the insect defence polypeptides, which could be exploited in drugs design against these pathogens
Anti-Legionella dumoffii activity of Galleria mellonella defensin and apolipophorin III
The gram-negative bacterium Legionella dumoffii is, beside Legionella pneumophila, an etiological agent of Legionnaires’ disease, an atypical form of pneumonia. The aim of this study was to determine the antimicrobial activity of Galleria mellonella defense polypeptides against L. dumoffii. The extract of immune hemolymph, containing a mixture of defense peptides and proteins, exhibited a dose-dependent bactericidal effect on L. dumoffii. The bacterium appeared sensitive to a main component of the hemolymph extract, apolipophorin III, as well as to a defense peptide, Galleria defensin, used at the concentrations 0.4 mg/mL and 40 μg/mL, respectively. L. dumoffii cells cultured in the presence of choline were more susceptible to both defense factors analyzed. A transmission electron microscopy study of bacterial cells demonstrated that Galleria defensin and apolipophorin III induced irreversible cell wall damage and strong intracellular alterations, i.e., increased vacuolization, cytoplasm condensation and the appearance of electron-white spaces in electron micrographs. Our findings suggest that insects, such as G. mellonella, with their great diversity of antimicrobial factors, can serve as a rich source of compounds for the testing of Legionella susceptibility to defense-related peptides and proteins
Choline supplementation sensitizes Legionella dumoffii to Galleria mellonella apolipophorin III
Proline-Rich Antimicrobial Peptides in Medicinal Maggots of Lucilia sericata Interact With Bacterial DnaK But Do Not Inhibit Protein Synthesis
In the search for new antibiotics to combat multidrug-resistant microbes, insects offer a
rich source of novel anti-infectives, including a remarkably diverse array of antimicrobial
peptides (AMPs) with broad activity against a wide range of species. Larvae of the
common green bottle fly Lucilia sericata are used for maggot debridement therapy, and
their effectiveness in part reflects the large panel of AMPs they secrete into the wound. To
investigate the activity of these peptides in more detail, we selected two structurally
different proline rich peptides (Lser-PRP2 and Lser-PRP3) in addition to the a-helical
peptide Lser-stomoxyn. We investigated the mechanism of anti-Escherichia coli action of
the PRPs in vitro and found that neither of them interfered with protein synthesis but both
were able to bind the bacterial chaperone DnaK and are therefore likely to inhibit protein
folding. However, unlike Lser-stomoxyn that permeabilized the bacterial membrane by 1%
at the low concentration (0.25 µM) neither of the PRPs alone was able to permeabilize E.
coli membrane. In the presence of this Lser-stomoxyn concentration significant increase in
anti-E. coli activity of Lser-PRP2 was observed, indicating that this peptide needs specific
membrane permeabilizing agents to exert its antibacterial activity. We then examined the
AMPs-treated bacterial surface and observed detrimental structural changes in the
bacterial cell envelope in response to combined AMPs. The functional analysis of insect
AMPs will help select optimal combinations for targeted antimicrobial therap
Studies on the interactions of neutral Galleria mellonella cecropin D with living bacterial cells
Antifungal activity of anionic defense peptides : insight into the action of Galleria mellonella anionic peptide 2
Control of Propionibacterium acnes by natural antimicrobial substances: Role of the bacteriocin AS-48 and lysozyme
We report the high susceptibility of several clinical isolates of Propionibacterium acnes from different
sources (skin, bone, wound exudates, abscess or blood contamination) to the head-to-tail cyclized
bacteriocin AS-48. This peptide is a feasible candidate for further pharmacological development against
this bacterium, due to its physicochemical and biological characteristics, even when it is growing in a
biofilm. Thus, the treatment of pre-formed biofilms with AS-48 resulted in a dose- and time-dependent
disruption of the biofilm architecture beside the decrease of bacterial viability. Furthermore, we
demonstrated the potential of lysozyme to bolster the inhibitory activity of AS-48 against P. acnes,
rendering high reductions in the MIC values, even in matrix-growing cultures, according to the results
obtained using a range of microscopy and bioassay techniques. The improvement of the activity of
AS-48 through its co-formulation with lysozyme may be considered an alternative in the control of P.
acnes, especially after proving the absence of cytotoxicity demonstrated by these natural compounds
on relevant human skin cell lines. In summary, this study supports that compositions comprising the
bacteriocin AS-48 plus lysozyme must be considered as promising candidates for topical applications
with medical and pharmaceutical purposes against dermatological diseases such as acne vulgaris.This research was funded by a grant
from the Spanish Ministry of Economy and Competitiveness (SAF2013-48971-C2-1-R that included funds from
European Regional Development, ERDF), and the Research Group General (BIO160, UGR)
Lysozyme enhances the bactericidal effect of BP100 peptide against Erwinia amylovora, the causal agent of fire blight of rosaceous plants
The Intestinal Microbiota of Hermetia illucens Larvae Is Affected by Diet and Shows a Diverse Composition in the Different Midgut Regions
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