Kannurin, a novel lipopeptide from Bacillus cereus strain AK1: isolation, structural evaluation and antifungal activities

Abstract

Aim: This study was performed to isolate and characterize novel antifungal lipopeptide from Bacillus cereus. Methods and Results: Elucidation of its chemical structure was carried out by electrospray ionization mass spectra (ESI-MS) and Fourier transform infrared spectroscopy (FT-IR). The compound is a cyclic heptapeptide and composed of amino acids, Leu-Asp-Val-Leu-Leu-Leu-Leu. The in vitro activity of Kannurin against various pathogenic yeasts was assessed by CLSI M27-A and moulds by M38-A. It demonstrated broad-spectrum, fungicidal activity against clinically relevant yeasts and moulds. Kannurin exhibited low haemolytic activity and remained active over a wide pH and temperature range. In addition, Kannurin did not bind with melanin particles and was as active in inhibiting biofilms. Conclusions: An antifungal surfactin-like lipopeptide produced by Bacillus cereus strain AK1 was purified and chemically characterized. We propose to name this lipopeptide compound 'Kannurin'. To our knowledge, this is the first report of Bacillus cereus producing surfactin-like lipopeptide antibiotic with stronger antifungal activity. Significance and Impact of the Study: Our results provide a valuable contribution towards a better understanding of the lipopeptide of Bacillus cereus. Moreover, it raises the possibility of using as an alternative antibiotic in clinical medicine.

Purification of Antilisterial Peptide (Subtilosin A) from Novel Bacillus tequilensis FR9 and Demonstrate Their Pathogen Invasion Protection Ability Using Human Carcinoma Cell Line

“…The FTIR spectra of Subtilosin A showed peaks at 1540, 1644, and 3233 cm -1 which confirms the existence of peptide bonds in the sample ( Figure 4 ). The intense peak at 1644 cm -1 confirms the presence of primary amino group (amide I) with C = O stretch (Ajesh et al, 2013). Similarly, another intense peak at 1181 cm -1 revealed the presence of secondary amino group (amide II) having C-N stretch.…”

“…Purified BLIS was mixed with KBr (spectroscopic grade) and pellet was prepared with the size of about 10–13 mm diameter and 1 mm thickness. Sample was scanned in transmission mode with a resolution of 4 cm -1 at 4000–400 cm -1 range and functional groups were compared with previously published literature (Coates, 2000; Ajesh et al, 2013). …”

Biofilm Formation by Cryptococcus neoformans

“…Amphotericin B and caspofungin mediated a significant reduction of the metabolic activity of C. neoformans cells consistent with their fungicidal properties, but the concentrations used were high and above achievable levels in vivo after systemic administration and their susceptibility to these drugs was further reduced if cryptococcal cells contained melanin. Moreover, an antifungal surfactant-like lipopeptide, kannurin, produced by Bacillus cereus showed moderate effects against cryptococcal biofilms (34).…”

Bacteriocinogenic potential of a probiotic strain Bacillus coagulans [BDU3] from Ngari

“…Absorption valley at 2936 cm −1 results from C H stretching indicates the existence of aliphatic chain. The peak at 1415 cm −1 arises from the amide II band which results from the deformation of N H bond combined with C N Stretching molecule [40]. The peaks at 1645 cm −1 and 1506 cm −1 indicate the existence of amide I and amide II [41].…”