Newly-Discovered Soil Bacterium May Fight Dangerous Microbes

Antibiotic resistance in bacteria is a serious problem at the moment. As microbes become resistant to the effects of the antibiotics that once killed them, some dangerous organisms are becoming much more difficult to destroy. If this process continues, there could be major and even tragic consequences for our health. Researchers have discovered a few new species or strains of bacteria in soil that offer some hope in the form of the chemicals that they produce. A multinational team at Swansea University in Wales has found a new species of bacterium in Irish soil that destroys some potentially very harmful bacteria in lab equipment.

Streptomyces sp.

Photo credit: CDC Public Health Image Library, public domain license

Special Soil

The Irish soil sample was obtained from an area known as the Boho Highlands, which is located in Fermanagh in Northern Ireland. The region contains alkaline soil. It's interesting that the soil has a reputation for healing abilities. In the past, people used to wrap some of the earth in cloth and apply the bundle to injured areas. The area was once inhabited by druids. It's important to note that harmful as well as helpful organisms live in soil, so applying soil to injuries could be dangerous. Certain components of the soil might be helpful, however.

In general, scientists have paid little attention to folk medicine, relying on experimental discoveries in the lab instead. Some scientists are now exploring materials and substances  traditionally believed to have medicinal benefits by different cultures, a subject known as ethnopharmacology. One of the scientists involved in the Boho Highlands research once lived in the area and was aware of the soil's reputation. Exploring unusual sources of help (according to current medical beliefs) seems like a good idea in our fight against harmful bacteria.

A New Version of Streptomyces

The Streptomyces genus of bacteria contains many species, some of which have proved to be very valuable for us. A large number of antibiotics have come from various members of the genus. One of the earliest was streptomycin. The bacteria exist as filaments and produce chains of spores, as shown in the photo above. Though their morphology may remind people of fungi, they are true bacteria. They are chiefly found in the soil and amongst decaying plants. They are known for the "earthy" odour that they produce. The smell is caused by a chemical called geosmin that is released when the bacteria die. 

The researchers who examined the Irish soil were looking for a new species or strain of Streptomyces, and they found one. The researchers have named the organism Streptomyces sp. myrophorea. They say that its closest known relative has “57% of genome relatedness.” The species name is not written in italics because at the moment it hasn’t been officially recognized as a new species. The bacterium releases a pleasant scent resembling that of oil of wintergreen. Its species name comes from the Greek myro, which means fragrance, and phorea, which means carrier.

The new bacterium inhibited the growth of four out of six major multi-drug resistant pathogens (microbes that cause disease), including:

·        vancomycin-resistant Enterococcus faecium

·        methicillin-resistant Staphylococcus aureus, or MRSA

·        Klebsiella pneumoniae

·        carbapenum-resistant Acinetobacter baumannii

The major drug-resistant pathogens are so important that a special collective name is used to refer to them. The ESKAPE pathogens are Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and species of Enterobacter.

Gram Positive and Negative Bacteria

The researchers found that the newly-discovered soil bacterium inhibited both gram-positive and gram-negative bacteria. This is important because gram-negative bacteria are usually harder to kill. The scientists don’t know the identity of the bacterial chemical that is harming the pathogens. They are investigating this question, however.

Gram-positive bacteria (such as Streptomyces) are covered by a cell membrane, which is in turn covered by a cell wall. Gram-negative ones have a inner cell membrane and a cell wall, but they also have another membrane outside of the wall. Unfortunately, the structure of their cell covering protects them from many antibiotics.

Gram negative and positive bacteria were given their designation due to their different behaviours during a staining process known as the Gram stain test. Gram-positive bacteria appear pink after the process and gram-negative bacteria look violet. The different colours are due to the different nature of the layers around the cell. The staining process is named after Hans Christian Gram, who created it in 1884.

Hopeful Research

The research is interesting and hopeful. It was carried out in lab equipment, however, not in a living organism. Results inside the body are sometimes different from those in laboratory containers. Nevertheless, investigators are finding some interesting soil bacteria that are potentially useful in the fight against antibiotics. The new species of Streptomyces may be one of them.

The researchers involved in the Boho highlands research say that they have found other bacteria in the soil that make antibiotics. They hope that these may fight additional species of pathogens.

References

Bacteria in Irish soil halts growth of superbugs from the Eurekalert news service

Gram staining information from Carleton College