Lipopeptides constitute a structurally diverse group of metabolites produced by various bacterial and fungal genera. In the past decades, research on lipopeptides has been fueled by their antimicrobial, antitumour, immunosuppressant and surfactant activities. However, the natural functions of lipopeptides in the lifestyles of the producing microorganisms have received considerably less attention. The substantial structural diversity of lipopeptides suggests that these metabolites have different natural roles, some of which may be unique to the biology of the producing organism. This review gives a detailed overview of the versatile functions of lipopeptides in the biology of Pseudomonas and Bacillus species, and highlights their role in competitive interactions with coexisting organisms, including bacteria, fungi, oomycetes, protozoa, nematodes and plants. Their functions in cell motility, leading to colonization of novel habitats, and in the formation and development of highly structured biofilms are discussed in detail. Finally, this review provides an update on lipopeptide detection and discovery as well as on novel regulatory mechanisms and genes involved in lipopeptide biosynthesis in these two bacterial genera.

Natural functions of lipopeptides from Bacillus and Pseudomonas: more than surfactants and antibiotics

The rapid onset of resistance reduces the efficacy of most conventional antimicrobial drugs and is a general cause of concern for human well-being. Thus, there is great demand for a continuous supply of novel antibiotics to combat this problem. Bacteria-derived antimicrobial peptides (AMPs) have long been used as food preservatives; moreover, prior to the development of conventional antibiotics, these AMPs served as an efficient source of antibiotics. Recently, peptides produced by members of the genus Bacillus were shown to have a broad spectrum of antimicrobial activity against pathogenic microbes. Bacillus-derived AMPs can be synthesized both ribosomally and nonribosomally and can be classified according to peptide biosynthesis, structure, and molecular weight. The precise mechanism of action of these AMPs is not yet clear; however, one proposed mechanism is that these AMPs kill bacteria by forming channels in and (or) disrupting the bacterial cell wall. Bacillus-derived AMPs have potential in the pharmaceutical industry, as well as the food and agricultural sectors. Here, we focus on Bacillus-derived AMPs as a novel alternative approach to antibacterial drug development. We also provide an overview of the biosynthesis, mechanisms of action, applications, and effectiveness of different AMPs produced by members of the Bacillus genus, including several recently identified novel AMPs.

Antimicrobial peptides of the genus Bacillus: a new era for antibiotics.

Emergence of community-acquired methicillin-resistant Staphylococcus aureus USA 300 clone as the predominant cause of skin and soft-tissue infections

Current microbial inhibition strategies based on planktonic bacterial physiology have been known to have limited efficacy on the growth of biofilm communities. This problem can be exacerbated by the emergence of increasingly resistant clinical strains. All aspects of biofilm measurement, monitoring, dispersal, control, and inhibition are becoming issues of increasing importance. Biosurfactants have merited renewed interest in both clinical and hygienic sectors due to their potential to disperse microbial biofilms in addition to many other advantages. The dispersal properties of biosurfactants have been shown to rival those of conventional inhibitory agents against bacterial and yeast biofilms. This makes them suitable candidates for use in new generations of microbial dispersal agents and for use as adjuvants for existing microbial suppression or eradication strategies. In this review, we explore aspects of biofilm characteristics and examine the contribution of biologically derived surface-active agents (biosurfactants) to the disruption or inhibition of microbial biofilms.

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Microbial biofilms: biosurfactants as antibiofilm agents

Surfactin, a bacterial cyclic lipopeptide, is produced by various strains of Bacillus subtilis and is primarily recognized as one of the most effective biosurfactants. It has the ability to reduce surface tension of water from 72 to 27 mN/m at a concentration as low as 0.005 %. The structure of surfactin consists of seven amino acids bonded to the carboxyl and hydroxyl groups of a 14-carbon fatty acid. Surfactin possesses a number of biological activities such as the ability to lyse erythrocytes, inhibit clot formation, lyse bacterial spheroplasts and protoplasts, and inhibit cyclic 3,5-monophosphate diesterase. The high cost of production and low yields have limited its use in various commercial applications. Both submerged and solid-state fermentation have been investigated with the mutational approach to improve the productivity. In this review, current state of knowledge on biosynthesis of surfactin, its fermentative production, purification, analytical methods and biomedical applications is presented.

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Surfactin – A Review on Biosynthesis, Fermentation, Purification and Applications

Bacillus polyfermenticus KJS-2 (BP-KJS-2) was used to produce a lipopeptide-type surfactin. To accomplish this, a surfactin-producing BP-KJS-2 was fermented by soybeans. The surfactin was then purified by a procedure including ethanol treatment and preparative chromatography. Next, the biochemical structure of the purified surfactin was analyzed by electrospray ionization mass spectrometry (ESI-MS) and high-resolution ESI Q-Tof mass spectrometry (Q-Tof MS). In addition, the masses of the four peaks were determined to be 1007, 1021, 1035, and 1049 m/z revealing that the compound was mixture with quasi-molecular ions. Taken together, these findings indicated that the lipopeptide had a cyclic structure and amino acid composition of Gln-Leu-Leu-Leu-Val-Asp-Leu-Leu, and that the major lipopeptide product of BP-KJS-2 is the surfactin isoform. In addition, this lipopeptide showed strong antimicrobial activity against bacteria at the level of 0.05 mg/mL.

Isolation and characterization of surfactin produced by Bacillus polyfermenticus KJS-2.

The principal objective of this study was to evaluate the antibacterial activities of macrolactin A (MA) and 7-O-succinyl macrolactin A (SMA) generated from Bacillus polyfermenticus KJS-2 against vancomycin-resistant enterococci (VREs) and methicillin-resistant Staphylococcus aureus. The minimal inhibitory concentrations (MICs) of MA and SMA against VREs were 16 and 2∼1 μg/mL, respectively, and the MICs of MA and SMA against methicillin-resistant Staphylococcus aureus were 2 and < 0.25 μg/mL, respectively. Their MIC values were comparable or superior to those of teicoplanin. In evaluating the inhibitory effects of intestinal VRE colonization in mice, the oral MA and SMA effected a rapid inhibition of intestinal VRE colonization in mice, and the intraperitoneal SMA also inhibited VRE colonization, whereas intraperitoneal MA did not.

Antibacterial activities of macrolactin A and 7-O-succinyl macrolactin A from Bacillus polyfermenticus KJS-2 against vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus.

One of the strains of the Bacillus mojavensis group, Bacillus mojavensis KJS-3 (B. mojavensis KJS-3), which has been demonstrated to play a role in protecting plants against diseases as a bacterial endophyte and in reducing the accumulation of mycotoxins generated by an endophytic fungus, was recently discovered in food waste. In this study, the identification and characterization of B. mojavensis KJS-3 was performed via TEM analysis, API-zym test, API 50 CHB test, assays of catalase and oxidase activity, lactic acid production, stability under various conditions, antibiotic susceptibility, and cellular fatty acid composition. The overall results of this study demonstrate that B. mojavensis KJS-3 may have great potential as a probiotic product, as this bacterium is quite stable in somewhat harsh environments. B. mojavensis KJS-3 was positive on oxidase and catalase tests, and the conversion rate of glucose to lactic acid was 58.9%. Finally, anteiso-C15:0 (43.10%) was identified as the major fatty acid.

Characterization of Bacillus mojavensis KJS-3 for industrial applications

Cultivated wild ginseng has a variety of pharmacological effects. The aim of this study was to investigate the effects of cultivated wild ginseng extracts (CWGE) on apoptosis. CWGE showed the ability to protect hormone production (testosterone and progesterone from in vitro results) in TM3 Leydig and TM4 Sertoli cells damaged by Bisphenol A (BPA). CWGE also showed the ability to protect production of testosterone (7.24%, P<0.05), plasma luteinizing hormone (LH) (32.67%, P<0.05), and follicle-stimulating hormone (FSH) (37.34%, P<0.05) compared to the control and BPA-only groups. Reduction of apoptotic protein expression and induction of anti-apoptotic protein expression was observed in cells and rats pretreated with CWGE. These proteins are expressed through the ERK and p38 signalling pathways. In addition, CWGE might be a useful herbal medicine of cellular defense agents as our results in cells and animals.

Cultivated wild ginseng extracts upregulate the anti-apoptosis systems in cells and mice induced by bisphenol A

Recent studies have reported the relationship between reduced sperm counts and male infertility. The effects of cultivated wild ginseng extracts, which include ginsenosides, on cellular antioxidant activities were studied in testicular cells and animal models. In a study of rats, the weight of testis-right (15.38%, P<0.05) and testis-left (16.98%, P<0.05) in group D (cultivated wild ginseng extracts with bisphenol A) increased in comparison with group A (only bisphenol A). Reactive oxygen species of TM3 Leydig and TM4 Sertoli cells treated with bisphenol A significantly increased, by 36-41%, compared to the controls. Cultivated wild ginseng extracts at 10 and 25 μg/mL significantly increased the expression of catalase in TM3 cells, and catalase, superoxide dismutase 1, and glutathione peroxidase enzymes in TM4 cells. The induction of expression of catalase and superoxide dismutase 1 by cultivated wild ginseng extracts in rats occurs via the ERK and p38 pathways. Cultivated wild ginseng extracts also ameliorated the histopathological changes induced by bisphenol A in the testis.

Jae Seon Kang

Papers

Isolation and characterization of surfactin produced by Bacillus polyfermenticus KJS-2.

Antibacterial activities of macrolactin A and 7-O-succinyl macrolactin A from Bacillus polyfermenticus KJS-2 against vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus.

Characterization of Bacillus mojavensis KJS-3 for industrial applications

Cultivated wild ginseng extracts upregulate the anti-apoptosis systems in cells and mice induced by bisphenol A

Testicular antioxidant mechanism of cultivated wild ginseng extracts