Ameur Cherif

By Afef Najjari, Hiba Mejri, Marwa Jabbari, Haitham Sghaier, Ameur Cherif and Hadda-Imene Ouzari

Members of extremely halophilic archaea, currently consisting of more than 56 genera and 216 species, are known to produce their specific bacteriocin-like peptides and proteins called halocins, synthesized by the ribosomal pathway. Halocins are diverse in size, consisting of proteins as large as 35 kDa and peptide “microhalocins” as small as 3.6 kDa. Today, about fifteen halocins have been described and only three genes, halC8, halS8 and halH4, coding C8, S8 and H4 halocins respectively have been identified. In this study, a total of 1858 of complete and nearly complete genome sequences of Halobacteria class members were retrieved from the IMG and Genbank databases and then screened for halocin encoding gene content, based on the BLASTP algorithm. A total of 61 amino acid sequences belonging to three halocins classes (C8, HalH4 and S8) were identified within 15 genera with the abundance of C8 class. Phylogenetic analysis based on amino acids sequences showed a clear segregation of the three halocins classes. Halocin S8 was phylogenetically more close to HalH4. No clear segregation on species and genera levels was observed based on halocin C8 analysiscontrary to HalH4 based analysis. Collectively, these results give an overview on halocins diversity within halophilic archaea which can open new research topics that will shed light on halocins as marker for haloarchaeal phylogentic delineation.

Part of the book: Extremophilic Microbes and Metabolites

By Awatef Ouertani, Amor Mosbah and Ameur Cherif

In recent years the rapid emergence of drug resistant microorganisms has become a major health problem worldwide. The number of multidrug resistant (MDR) bacteria is in a rapid increase. Therefore, there is an urgent need to develop new antimicrobial agent that is active against MDR. Among the possible candidates, antimicrobial peptides (AMPs) represent a promising alternative. Many AMPs candidates were in clinical development and the Nisin was approved in many food products. Exact mechanism of AMPs action has not been fully elucidated. More comprehensive of the mechanism of action provide a path towards overcoming the toxicity limitation. This chapter is a review that provides an overview of bacterial AMPs named bacteriocin, focusing on their diverse mechanism of action. We develop here the structure–function relationship of many AMPs. A good understanding of AMPS structure–function relationship can helps the scientific in the conception of new active AMPs by the evaluation of the role of each residue and the determination of the essential amino acids for activity. This feature helps the development of the second-generation AMPs with high potential antimicrobial activity and more.

Part of the book: Insights on Antimicrobial Peptides

By Meriem Msaad Guerfali, Haytham Hamden, Kamel Charaabi, Salma Fadhl, Amor Mosbah and Amer Cherif

The Mediterranean fruit fly Ceratitis capitata (medfly) is a major pest throughout the world and one of the most destructive. Several strategies for controlling this pest have been proposed, including the sterile insect technique (SIT). The SIT’s effectiveness against the medfly is well documented. Sterile medflies, on the other hand, can perform poorly. Reduced mating compatibility and mating competitiveness in the field may be caused by genetic and symbiotic differences between natural and laboratory medfly populations. Probiotic gut symbionts have been shown to facilitate control strategies and improve male medfly fitness. They are equally effective in the live and inactivated forms when administered to medfly adults or larvae. They have been shown to modulate a large set of inducible effector molecules including antimicrobial peptides (AMP) and stress-responsive proteins. The selection procedures of probiotics for their use in the medfly rearing process are reviewed, and other pathways for selection are proposed based on recent in silico studies. This chapter summarizes the most relevant evidence from scientific literature regarding potential applications of probiotics in medfly as an innovative tool for biocontrol, while also shedding light on the spectrum of symbiotic relationships in medfly that may serve as a powerful symbiotic integrative control approach.

Part of the book: Advances in Probiotics for Health and Nutrition

By Salma Kloula Ben Ghorbal, Sana Dhaouadi, Sana Bouzenbila, Ameur Cherif and Ramzi Boubaker Elandoulsi

Biofilms formed by multidrug resistant (MDR) bacteria like methicillin-resistant Staphylococcus aureus (MRSA) and others are the main causes of infections that represent a serious public health issue. Persistent MDR infections are mostly derived from biofilm formation which in turn leads to resistance to conventional antimicrobial therapy. Inhibition of bacterial surface attachment is the new alternative strategy without affecting the bacterial growth. Thus, the discovery of compounds that interfere with biofilm production, virulence factors release and quorum sensing (QS) detection in pathogens is a promising processus. Among these compounds, natural and synthetic molecules are a compelling alternative to attenuate pathogenicity. The combination of these compounds with antibiotics makes the bacteria more vulnerable to the later, once used alone. This combination can restore antibiotic effectiveness against MDR bacteria. Among these molecules, 3-phenylpropan-1-amine (3-PPA) has been found to inhibit Serratia marcescens biofilm formation, PAβN has been proven to inhibit biofilm prodcution in A. baumannii, while brominated Furanone C-30 has been reported to be a potent inhibitor of the QS system and P. aeruginosa biofilm. Therefore, the combination between biofilm-inhibitors and antibiotics represents a promising strategy to mitigate antibiotic resistance in MDR pathogens, which has become a major threat to public healthcare around the globe.

Part of the book: Recent Advances in Bacterial Biofilm Studies