Marine Actinobacteria,

the Microbial Pearl of the Sea

While the sea is a host to ancient hidden treasures, perhaps the best treasure yet is a ticket to good health. With antibiotic resistance on the rise, scientists are looking for new microbes as a source for the development of new antibiotics and other medication. A recent study has shown that marine Actinobacteria, bacteria found in seaweed, may contain the antimicrobial properties scientists have been looking for.

Marine Actinobacteria: precious microbes from the sea

Actinobacteria are microorganisms that have the characteristics of both bacteria and fungi. Actinobacteria produce secondary metabolites that may be used to develop future drugs against serious diseases and, for this reason, have always been of high pharmacological interest. In fact, a number of antibiotics have been discovered from terrestrial Actinobacteria, which can be found in soil. Land species of these microbes, however, are beginning to run out as more and more diseases are antibiotic resistant and researchers have begun a new quest in the depths of the sea.

The marine environment is an unexploited source of new Actinobacteria and, consequently, also of new metabolites. Marine Actinobacteria is mostly found in sediments on the sea floor, but is also found in organisms that live and feed on the sea floor, such as seaweed. Two recent studies have confirmed the presence of novel Actinobacteria in different marine environments and habitats that is capable of producing various new metabolites and, thus, possibly even new drugs.

Marine Actinobacteria

Breakthroughs in marine drug research

Recent studies in Portugal and the Philippines could be the sources of another breakthrough in the development of new antibiotics and other medication.

Research carried out by the Interdisciplinary Centre of Marine and Environmental Research (CiiMAR) in Portugal reveals that a common species of seaweed, Laminaria ochroleuca, is a rich source of Actinobacteria that may have antimicrobial and anticancer properties for the development of new drugs. “The brown alga L. ochroleuca forms complex structures called kelp forests, which are among the most diverse and productive ecosystems in the world, but until now, no-one had characterized the Actinobacteria that live inside L. ochroleuca”, said senior author of the study, Dr. Maria de Fátima Carvalho, a researcher at CiiMAR.

Carvalho’s research team analyzed samples of L. ochroleuca, which were collected off the coast of northern Portugal and then cultured in a lab for six weeks. Ninety Actinobacterial extracts were isolated from the samples and screened for antimicrobial and anticancer activity. Forty-five of these extracts inhibited the growth of harmful bacteria, such as Candida albicans and Staphylococcus aureus, bacteria that can cause skin infections. Some extracts proved effective even at very low concentrations, making them ideal for the development of new drugs, and others showed some anticancer activity. “Seven of the extracts inhibited growth of breast and particularly nerve cell cancers, while having no effect on noncancer cells,” said Dr. Carvalho. The scientists at CiiMAR concluded that the seaweed L. ochroleuca contains high levels of Actinobacteria with potential cancer-fighting and antimicrobial properties. The study was published in Frontiers in Microbiology.

Another marine sediment project in search of new drug candidates was carried out in the Philippines. “We explored the marine sediments in the Philippine archipelago for antibiotics-producing bacteria,” says Dr. Doralyn Dalisay, head of Research and Development at the University of San Agustin – Center for Chemical Biology and Biotechnology (USA-C2B2) in Iloilo. Actinobacteria was successfully extracted from the sediment samples and Dalisay’s team identified 38 bacterial isolates to be studied in hopes of developing at least one super antibiotic drug. According to Dalisay, 7 of the 38 isolates show very strong activity against two or three antibiotic-resistant “superbugs”. Other 8 isolates show potential in fighting off multi-drug resistant staphylococcus aureus, pneumonia, heart valve infections and bone infections. “Our (C2B2) lab in the University of San Agustin is looking at new antibiotics from Actinobacteria dwelling in the marine sediments. So, this is really different, it’s a different species, a different organism. When you say it’s different, that means there could be new antibiotics,” Dalisay said.

Marine ecosystems remain largely unexplored, but this new research demonstrates that the sea may represent an important source for the discovery of new Actinobacteria and, hence, bioactive compounds capable of fighting off difficult and antibiotic resistant diseases. There is still much to be learned from the sea, but the biodiversity of marine Actinobacteria brings new hope for the future of antibiotics and many other important medicines.

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