Chillingly in the news these days is anthrax. Iraq's Saddam Hussein is allegedly fixing to ferment this deadly soil bacterium as top gun in his hidden germ-warfare arsenal.
Bacillus anthracis, the microorganism that causes anthrax, has a mixed history. In the 17th and 18th centuries, anthrax decimated both man and beast in European pandemics.
Then in the late 19th century, Louis Pasteur, hero of the vaccine against the rabies virus, produced the first effective immunization against a bacterium, namely, B. anthracis. This feat launched the twin sciences of bacteriology and immunology.
Early in our own 20th century, the U.S., Britain and other countries cultured the anthrax germ for possible use in warfare, before biological weapons got a bad name.
Now the United Nations arms inspectors strongly suspect that Iraq's weapons developers are threatening their country's neighbors with anthrax, in the event of hostilities.
Of possible relevance, French molecular geneticist Antoine Danchin told BioWorld Today: "In 1988, we were the first to clone the adenylate cyclase toxin of B. anthracis. When we reported this at a meeting was the only time I ever met Iraqi scientists. They seemed interested."
B. Subtilis Harmless To People
The closest molecular cousin of B. anthracis is Bacillus subtilis, which has a 40-year-old history of its own. For one thing, it used to contaminate Pasteur's laboratory flasks.
Like B. anthracis, B. subtilis is a Gram-positive soil bacterium, which forms spores to hibernate in times of stress or famine. Unlike the anthrax pathogen, it is harmless to humans and other mammals.
When biotechnology was busy getting invented a quarter-century ago, industrial researchers looked longingly at B. subtilis as a candidate host organism for cloning and expressing genes of interest. It had one apparent advantage over front-running Escherichia coli, a Gram-negative bacterium, which could not secrete recombinant products beyond its outer cell wall into the medium. B. subtilis could.
E. coli has proved a bit of a letdown to industry. As a recombinant horn of plenty, it was beset by lack of specificity, an expensive appetite for nutrients and, of course, difficulty in recovering its end-products in the external medium. But E. coli has remained the gold-standard workhorse of both industry and academia in moving biotechnology forward.
B. subtilis, on the other hand, has a limited commercial capacity for producing industrial enzymes (such as amylase) in quantity, as well as high-value small molecules, such as antibiotics (so far, bacitracin).
Today's issue of Nature, dated Nov. 20, 1997, reports in its lead article: "The complete genome sequence of the Gram-positive bacterium Bacillus subtilis."
Its list of co-authors numbers 151 collaborators, from a consortium of 46 centers in Europe and Japan. Its senior author, Danchin, and first author, Frank Kunst, are both from the Pasteur Institute, in Paris.
In contrast, Science announced only three months ago: "The complete genome sequence of Escherichia coli K-12." (See BioWorld Today, Sept. 5, 1997, p. 1.) That comparable feat listed 17 co-authors from three U.S. centers, plus one in Mexico.
Here is how the two genomes stack up:
Base pairs: B. subtilis, 4, 214,810. E coli, 4,639,221
Protein-encoding genes: B. subtilis, 4,100. E coli, 4,288
Genes of unknown function: B. subtilis, 42 percent. E coli, 38 percent.
"Our B. subtilis sequencing project," Danchin told BioWorld Today, "was from its start, in early 1987, beset by many political and financial constraints, as well as technical problems. By 1989, when we began to construct the first set of DNA libraries, we were a consortium of only five different centers, because the Americans couldn't be funded.
"At this time," he recounted, "we just constructed new means to walk on the chromosome; to start from known regions, go into adjacent regions and sequence them. This, in fact, was a very good thing, because it allowed us to have piecemeal sequencing, by distributing to the participating groups different regions in the bacterium's chromosome."
Besides "coordinating the scientific outcome of the project by handling all the data," he and his staff at Pasteur "constructed the whole database, so there is consistency in the annotation. In addition, we also sequenced 300 kilobases of the genome in my Regulation of Gene Expression Laboratory, which is a wet lab."
The consortium finished sequencing the final base pair at the end of April, Danchin recalled. "But at that time," he added, "we still had a lot of questions about verification. This project was done in many different labs, so the quality of the sequencing must vary, and we had to verify that. I think we had a better sequence by mid-July, when we announced its completion in Lausanne, Switzerland, at the biennial international Bacillus subtilis meeting."
Study Of Gene Function Under Way
Now he is starting to "identify the gene products of the various genes we have singled out from analysis of the chromosome. That is, we will inactivate the genes and try to identify their phenotypes. This should be completed more or less by the end of 1998, financed by a new consortium.
Among the many novel genomic characteristics revealed by the total sequencing of B. subtilis was discovery of genes encoding 10 latent bacteriophage precursors. "They comprise genes similar to the virulence genes we see in pathogenic Gram-positive microorganisms," Danchin said, "which are generating resistance to antibiotics. This means that B. subtilis, though not itself pathogenic, might become so, just by acquiring something nasty from outside."
This threat is on a par with the menace of biological warfare, suggests an observation by Harvard University molecular biologist Richard Losick. He wrote an editorial accompanying the Nature paper.
Losick told BioWorld Today that "a valuable legacy of this new total genome relates to B. subtilis being a model for Gram-positive bacteria. These include some microorganisms that are leading causes of death, and life-threatening infections. Many of them," he warned, "are becoming resistant to well-known antibiotics, and so threaten the existence of therapy against infections, especially in hospitals." *