An antibiotic substance produced by the spined soldier bug

spined soldier bug (Podisus maculiventris) attacking Mexican bean beetle larvae (Epilachna varivestis) (Photo Agricultural Research Service)
spined soldier bug (Podisus maculiventris) attacking Mexican bean beetle larvae (Epilachna varivestis) (Photo Agricultural Research Service)

An article published in the journal “Science Advances” describes a research on a substance produced by spined soldier bugs – species Podisus maculiventris – that could replace some antibiotics in the treatment of certain types of infections. A team of researchers from the University of Zurich and the ETH Zurich discovered that through a mechanism so far unknown this insect produces what was called thanatin. This substance is capable of attacking bac cell walls of bacteria such as the ones of the Escherichia coli family, which includes species that are developing increasing resistance to current antibiotics.

The problem of antibiotic resistance is becoming increasingly serious, so much so that there are already so-called superbugs, which can be resistant to various antibiotics. Years of misuse and abuse of these drugs led to a selection of mutants resistant to them and if no new remedies are found some expect a return of lethal outbreaks caused by these new strains.

Booming biotechnologies could help improve the effectiveness of antibiotics, but there are researchers who keep on studying the production of natural substances that can be used as drugs against some type of bacterial infection. The spined soldier bug is an insect already known because it’s a predator that hunts larvae of other species so they can be a remedy against certain pests, in fact there are companies that sell their eggs for this purpose.

An interdisciplinary team of chemists and biologists discovered a new potential substitute for various antibiotics. It’s a peptide, which is a molecule consisting of various amino acids joined by a specific bond called peptidic, that can prevent the formation of the outer walls of cell membranes. Gram-negative bacteria have a double cell membrane and the outer one has an important defensive role. Among its components there are lipopolysaccharides (LPS), so called because they are made up of a lipid part and a polysaccharide part and is essential for bacteria to survive.

The researchers succeeded in proving that thanatin interferes with the transport of LPS molecules in the process of formation of the bacteria’s outer cell membrane. John Robinson of the University of Zurich, one of the authors of this study, stated that it’s an unprecedented mechanism for an antibiotic that suggests ways to develop new molecules to be used as antibiotics to target dangerous pathogens. There are species of the Escherichia coli family that can be dangerous but are becoming increasingly resistant to antibiotics with the result that the infections they cause are becoming increasingly dangerous.

During the course of this study, an analysis of the development of thanatin-resistant mutants was also carried out because by now the evaluations of an antibiotic’s efficacy must be carried out trying to understand how long it takes for pathogenic bacteria to develop a resistance. Thanatin could really be a new frontier concerning antibiotic action and the researchers also pointed out that the study of its action contributes to a better understanding of its biological function in its natural context. Basically, there are various developments of new antibiotics through biotechnologies but the research of substances produced in nature are still essential.

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