Fewer than one percent of microbes around us will grow in a lab dish
For two centuries microbiologists learned about germs by growing them in culture. The catch is that fewer than one in a hundred microbes from ordinary soil or water will grow alone in a dish. Much of the microbial world was invisible until scientists started identifying organisms by their DNA instead.
Microbiology studies organisms too small to see, whether single cells, simple multicellular forms or things without cells at all. Its branches include virology, bacteriology, mycology and parasitology. The traditional toolkit was culture, staining and the microscope, but modern labs often identify bacteria by sequencing a single gene, 16S ribosomal RNA. Viruses have been counted both as extremely simple microbes and as very complex molecules, and virologists hunting for a slow virus instead uncovered prions, infectious proteins.
Who saw microbes first is debated. Robert Hooke recorded mould fruiting bodies under a microscope in the 1660s, and Antonie van Leeuwenhoek in Delft described bacteria in 1676 with single-lens microscopes he built himself. The Jesuit scholar Athanasius Kircher, who also designed early magic lanterns, may have beaten both, writing of countless worms in vinegar and milk; his 1658 study of plague correctly blamed microbes, although what he saw were probably blood cells.
The science matured in the 19th century. Ferdinand Cohn, a botanist, founded bacteriology, drew up the first bacterial classification and discovered endospores. Louis Pasteur disproved spontaneous generation and developed pasteurization and vaccines against anthrax, fowl cholera and rabies. Robert Koch proved that particular microbes cause particular diseases, set out his famous postulates and described the tuberculosis bacterium. Their medical focus missed most microbial diversity, which Martinus Beijerinck and Sergei Winogradsky revealed. Beijerinck discovered viruses through tobacco mosaic disease and invented enrichment culture, while Winogradsky showed how microbes drive soil chemistry and first isolated nitrogen-fixing bacteria.
Microbes are also workhorses. They ferment alcohol, vinegar and dairy foods, make antibiotics such as the aminoglycosides from Streptomyces, and supplied Taq polymerase for copying DNA. One species, Corynebacterium glutamicum, produces more than two million tonnes of amino acids a year, mainly glutamate and lysine.
Source: Microbiology
