An NYU School of Medicine researcher studying the human microbiome took a peek into a mini time machine earlier this week to obtain a better understanding of the evolution of bacteria. Martin Blaser, M.D., who serves as the chairman of the school’s department of medicine, opened a Pasteur tube that was sealed at both ends over 100 years ago.
The tube, which contained bacterial spores, had been placed in a cornerstone of a building being dedicated for Bellevue Hospital Medical College back in 1897. The building was recently demolished. The bacterial strain, originally called Bacillus aerogenes capsulatus but now known as Clostridium perfringens, is found on virtually all humans and was once associated with gangrene. The spores in the tube came from a 23 year old patient.
Dr. Blaser’s main interest in these old microorganism stems from the fact that they had lived during the pre-antibiotic era. “I want to know how antibiotics have affected the microbiome,” Dr. Blaser told GEN, referring to the entire community of microorganisms living within human beings. “Also, have antibiotics altered the composition of the metagenome (which comprises the entire range of microorganisms that make up the microbiome)?”
Dr. Blaser and his team are in the process of culturing the bacterial spores found in the tube. “We hope that they will grow out living bacterial organisms from which we can extract the DNA and subject it to whole genome sequencing,” he continued, adding that the scientists use 454 Life Science and Illumina sequencing systems.
He then plans to compare the DNA to that of modern members of this bacterial species to determine if there have been any substantial changes in the genome. “We’ll be looking closely at the modern strains to see if any large deletions have taken place or if we can detect the presence of antibiotic-resistant elements,” said Dr. Blaser.
If there is an overarching theme to Dr. Blaser’s research efforts it can be describe d as a concentration on the study of the biology of bacterial persistence in mammalian hosts. He first became involved in the field back in 1985 when he began studying Heliobacter pylori, which had been implicated in cases of chronic gastritis and ulcers. “It quickly became clear to me that this was the dominant organism in the stomach and that is was quite ancient,” he told GEN.
Dr. Blaser’s group is currently investigating the microbiomes of the skin and the human colon. “The focus in my laboratory is to explore the biology of H. pylori colonization and the nature of the interactions that lead to, or protect from, disease,” he remarked.
“Several avenues are being approached. We are examining the variation in particular oligosaccharide (Lewis) antigens on the H. pylori cell surface and the nature of the host forces that select for cells of particular phenotypes. Disciplines involved include molecular biology, genetics, and mathematics. We are using transgenic and knockout mice to test hypotheses related to both host factors and bacterial evolution.
“Other projects relate to restriction-modification systems that act as barriers to horizontal gene transfer and to a metastable ‘pathogenicity island’ in the H. pylori genome (cag island). A third area of work relates to recombination, endogenous mutation, and DNA repair to understand their roles and regulation in the generation of diversity.”