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To increase the level of adsorption of cadmium ions to the surface of Escherichia coli, we fused cyanobacterial metallothioneins, SmtA (from Synechococcus elongatus PCC 3601) and MtnA (from Synechococcus vulcanus) to the E. coli cell surface using a Lpp'-OmpA-based display system. E. coli strains expressing Lpp'-OmpA-SmtA-linker-ChBD (chitin-binding domain from Bacillus pumillus SG2 chitinase S; chiS) and Lpp'-OmpA-MtnA-linker-ChBD on their surface adsorbed more cadmium compared to the E. coli cells expressing only the Lpp'-OmpA-linker-ChBD hybrid. These constructs also were bound to chitin through their chitin-binding domain, allowing them to be immobilized on a chitin matrix. We assessed surface presentation of Lpp'-OmpA-SmtA-linker-ChBD, Lpp'-OmpA-MtnA-linker-ChBD, and Lpp'-OmpA-linker-ChBD using immunostaining. The Lpp'-OmpA-SmtA-linker-ChBD chimera adsorbed metal and was bound to chitin with the highest efficiency compared to the other chimeras, suggesting that it is an effective bioadsorbent. This is the first example of coupling metal adsorption with cell immobilization using a whole-cell bioadsorbent.

Given the emerging multidrug-resistant pathogens, the number of effective antimicrobial agents to deal with the threat of bacterial and fungal resistance has fallen dramatically. Therefore, the critical solution to deal with the missing effective antibiotics is to research new sources or new synthetic antibiotics. Natural products have different advantages to be considered antimicrobial agents. There are different natural sources for antimicrobial agents, such as bacteria, fungi, algae, slime molds, and plants. This article has focused on antibiotics from slime molds, especially Myxomycetes. The reason why slime molds have been chosen to be studied is their unique bioactive metabolites, especially over the past couple of decades. Some of those metabolites have been demonstrated to possess antibiotic activities. Hence, this article has focused on the potential of these creatures as an alternative source of antibiotics.