Rhamnolipids: diversity of structures, microbial origins and roles

Rhamnolipids are glycolipidic biosurfactants produced by various bacterial species. They were initially found as exoproducts of the opportunistic pathogen Pseudomonas aeruginosa and described as a mixture of four congeners: α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-Rha-C10-C10), α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoate (Rha-Rha-C10), as well as their mono-rhamnolipid congeners Rha-C10-C10 and Rha-C10. The development of more sensitive analytical techniques has lead to the further discovery of a wide diversity of rhamnolipid congeners and homologues (about 60) that are produced at different concentrations by various Pseudomonas species and by bacteria belonging to other families, classes, or even phyla. For example, various Burkholderia species have been shown to produce rhamnolipids that have longer alkyl chains than those produced by P. aeruginosa. In P. aeruginosa, three genes, carried on two distinct operons, code for the enzymes responsible for the final steps of rhamnolipid synthesis: one operon carries the rhlAB genes and the other rhlC. Genes highly similar to rhlA, rhlB, and rhlC have also been found in various Burkholderia species but grouped within one putative operon, and they have been shown to be required for rhamnolipid production as well. The exact physiological function of these secondary metabolites is still unclear. Most identified activities are derived from the surface activity, wetting ability, detergency, and other amphipathic-related properties of these molecules. Indeed, rhamnolipids promote the uptake and biodegradation of poorly soluble substrates, act as immune modulators and virulence factors, have antimicrobial activities, and are involved in surface motility and in bacterial biofilm development

Potential therapeutic applications of microbial surface-activecompounds

Numerous investigations of microbial surface-active compounds or biosurfactants over the past two decades have led to the discovery of many interesting physicochemical and biological properties including antimicrobial, anti-biofilm and therapeutic among many other pharmaceutical and medical applications. Microbial control and inhibition strategies involving the use of antibiotics are becoming continually challenged due to the emergence of resistant strains mostly embedded within biofilm formations that are difficult to eradicate. Different aspects of antimicrobial and anti-biofilm control are becoming issues of increasing importance in clinical, hygiene, therapeutic and other applications. Biosurfactants research has resulted in increasing interest into their ability to inhibit microbial activity and disperse microbial biofilms in addition to being mostly nontoxic and stable at extremes conditions. Some biosurfactants are now in use in clinical, food and environmental fields, whilst others remain under investigation and development. The dispersal properties of biosurfactants have been shown to rival that of conventional inhibitory agents against bacterial, fungal and yeast biofilms as well as viral membrane structures. This presents them as potential candidates for future uses in new generations of antimicrobial agents or as adjuvants to other antibiotics and use as preservatives for microbial suppression and eradication strategies

The regional component of the jargon of street groups of the 1980s and 1990s (based on the speech material of Yoshkar-Ola)

The work is devoted to the study of the vocabulary of youth groups in Yoshkar-Ola in 1980–1990. The purpose of this article is to characterize the local features of the language of Yoshkar-Ola youth unofficial groups. The research material was the jargon of participants in street gangs in the capital of the Republic of Mari El at the end of the twentieth century. The sources of language material were documentary literature, journalistic articles, dictionaries of substandard vocabulary and recordings of live speech of former group members. During the research, methods of linguistic observation and description, dictionary interpretation, and contextual analysis of lexical units were used. As a result of the study, the authors come to the conclusion that a number of jargons discussed in the article have become part of the unofficial microtoponymy of the city of Yoshkar-Ola. The likelihood of such lexical units appearing in dictionaries of non-literary vocabulary published by leading publishers is extremely low. The collected material contains information about the etymology of the unofficial toponymy of the city of Yoshkar-Ola, the communicative preferences of local youth and the linguistic realities of 1980–1990. The sublanguage of hooligan youth is very close in nature to Russian argot. A more detailed study of the jargon of street gang members may help change the uncritical attitude of Russian speakers towards the language of the criminal world

Structural characterization of 1,8-naphthalimides and in vitro microbiological activity of their Cu(II) and Zn(II) complexes

Two new 1,8-naphthalimide derivatives (NI1 and NI2) have been synthesized and characterized. The photophysical properties of the new compounds have been investigated in organic solvents of different polarity. It has been shown that both compounds are solvent depended. Cu(II) and Zn(II) complexes of NI2 were obtained and characterized by IR-NMR, fluorescence and EPR spectroscopy. The influence of different metal cations on the fluorescence intensity has been investigated in acetonitrile solution. Antimicrobial composite PLA-metal complexes materials have been obtained for the first time. Microbiological activity of both metal complexes has been investigated in vitro against different Gram-positive and Gram-negative bacteria and two yeasts. The various antimicrobial activities and the minimum inhibitory concentrations (MICs) of both complexes have been determined. The microbiological activity of composite materials PLA-metal complexes in thin polymeric film has also been investigated. The results suggest that the new metal complexes could find application in designing new antimicrobial preparations to control the spread of infections.COST CA15114 “Anti-MIcrobial Coating Innovations to prevent infectious diseases (AMICI)” is acknowledged for supporting the networking.Peer Reviewe

Antimicrobial, Antibiofilm and Cytotoxicity Activity of a New Acridine Hyperbranched Polymer in Solution and on Cotton Fabric

For the first time a fluorescent hyperbranched polymer modified with acridine (P1000-Acrid) was tested in vitro for antimicrobial activity against different model pathogens. The results showed strong activity of the compound against the used Gram-positive and Gram negative bacteria and yeasts. Cytotoxicity effect of P1000-Acrid has been studied towards HEp-2 cell line. The antibacterial finishing of cotton fabric treated with the P1000-Acrid was evaluated towards Grampositive and Gram-negative bacteria. It has been shown that the studied P1000-Acrid polymer reduces bacterial growth and prevents the formation of biofilm. The obtained results indicate that the studied P1000-Acrid hyperbranched polymer possess good antimicrobial potential with the greatest effectiveness against the used Gram-positive strains.The authors acknowledge Grant № KOCT 01/24-2017, Fund “Scientific Research, Ministry of Education and Science of Bulgaria. IG and PB also acknowledge COST CA15114 “Anti-MIcrobial Coating Innovations to prevent infectious diseases (AMICI)”.Peer Reviewe