Characterization of a New Mixture of Mono-Rhamnolipids Produced by Pseudomonas gessardii Isolated from Edmonson Point (Antarctica)

Abstract

Rhamnolipids (RLs) are surface-active molecules mainly produced by Pseudomonas spp. Antarctica is one of the less explored places on Earth and bioprospecting for novel RL producer strains represents a promising strategy for the discovery of novel structures. In the present study, 34 cultivable bacteria isolated from Edmonson Point Lake, Ross Sea, Antarctica were subjected to preliminary screening for the biosurfactant activity. The positive strains were identified by 16S rRNA gene sequencing and the produced RLs were characterized by liquid chromatography coupled to high resolution mass spectrometry (LC-HRESIMS) and liquid chromatography coupled with tandem spectrometry (LC-MS/MS), resulting in a new mixture of 17 different RL congeners, with six previously undescribed RLs. We explored the influence of the carbon source on the RL composition using 12 different raw materials, such as monosaccharides, polysaccharides and petroleum industry derivatives, reporting for the first time the production of RLs using, as sole carbon source, anthracene and benzene. Moreover, we investigated the antimicrobial potential of the RL mixture, towards a panel of both Gram-positive and Gram-negative pathogens, reporting very interesting results towards Listeria monocytogenes with a minimum inhibitory concentration (MIC) value of 3.13 µg/mL. Finally, we report for the first time the antimicrobial activity of RLs towards three strains of the emerging multidrug resistant Stenotrophomonas maltophilia with MIC values of 12.5 µg/mL.

Combining OSMAC Approach and Untargeted Metabolomics for the Identification of New Glycolipids with Potent Antiviral Activity Produced by a Marine Rhodococcus

“…SV2 SW medium (1.5% glucose, 1.5% glycerol, 1.5% peptone, 0.1% CaCO 3 in filtered natural sea water) differentiates from the other media used in this study mainly for the relatively high concentration of nutrients, such as glycerol, glucose and peptone, which could trigger the production of the new compounds. It is widely documented that glycerol induces bacterial biosurfactants production [26,[56][57][58], suggesting that this nutrient could play an important role in the production of succinic saccharide esters from Rhodococcus sp. I2R.…”

“…The obtained crude extracts were screened for biosurfactant activity using the CTAB (cetyltrimethylammonium bromide) agar method [26] to detect the production of anionic biosurfactants. The presence of such molecules is easily detected by the formation of dark blue halos.…”

Prevalence and Antibiotic Resistance Profile of Bacterial Pathogens in Aerobic Vaginitis: A Retrospective Study in Italy

“…Moreover, it is important to monitor the maternal colonization status of ESBL-producing bacteria. The presence of ESBL strains is a risk factor for transmission to the newborn and is associated with preterm birth and premature rupture of membranes (pPROM), which shows the need to revisit diagnostic guidelines and implement therapeutic approaches [ 26 , 27 , 28 ]. In addition to the very important aspect related to pregnancy birth rate, it is important to collect information on AV pathogens and their resistance profiles to prevent infections in women of childbearing age and safeguard them from the outcome of an AV pregnancy.…”

Outer Membrane Vesicles Derived from Klebsiella pneumoniae Influence the miRNA Expression Profile in Human Bronchial Epithelial BEAS-2B Cells

“…In addition, hemolysins, tyrosine kinase, heat-stable enterotoxins and heat-labile exotoxins participate in the pathogenicity [ 6 , 7 ]. K. pneumoniae rapidly acquires antibiotic resistance mechanisms making the selection of the appropriate antibiotic treatment more challenging [ 1 , 8 ]. Carbapenem resistance appears to have the greatest impact on the effectiveness of the treatment.…”