The field of microbiology was very limited until the discovery of the microscope, though it did exist in a very practical sense. Though scientists were ultimately wrong about what actually carried and transmitted the plague, for example, they were correct in hypothesizing that it came from an outside source. Between then and now, the microscope was developed, and has been improved upon more and more. Now we have a great classification scheme for prokaryotes (assuming bacteria). It follows the standard domain, kingdom, phylum, class, order, family, genus, and species. The standard for most eukaryotes is also the same for prokaryotic nomenclature, simply by using the genus and species for identification. Even today, as microarray machines can map entire microbial genomes, it is still usually the light microscope that gets every microbiologist started.
The world of microbiology is fairly new, as the microscopes did not have enough resolution or magnification to look at the microbial world of prokaryotes. In 1872, Ferdinand Cohn is credited with the first use of the word “Bacillus,” and together with Louis Pasteur and Robert Koch, is considered to be one of the forefathers of bacteriology. Up until this point, bacteria had largely just been a hypothesis. Pasteur went on to work on developing a way to attenuate bacteria and to study virulent pathogens, sometimes very unethically, in order to find vaccines. Koch spread his talent among many different facets of the this world, discovering and describing anthrax and tuberculosis, while at the same time working on ways to plate, screen and stain bacteria for inspection (American Society of Microbiology, 2015). By the turn of the century, most lethal bacteria had been identified, while in the case of Staphylococcus aureus, one of its primary toxins, PVL, had been described.
Light Microscopes are important in the “inspection” step of studying bacteria. With most types of bacteria, stains need to be used with light or fluorescent microscopes. The technique depends on what is being sought. Fast acid testing, for example, tests whether bacteria is present or not. Gram testing is fairly important, because once a researcher knows whether a bacteria is gram positive or negative, they know a lot of things about the cell structure of the bacteria being tested. The overall technique of staining is very straightforward: the bacteria needs to be permeable to dye molecules. Usually a bath of a very mild surfactant does the trick; the bacteria then needs to be fixated. Trying to look at bacteria with only 1000X magnification is very difficult unless they are made to be rigid; third, the bacteria need to be mounted. This can be done by direct growth of bacteria on the the slide, or by smearing; finally, the stain can be added and then washed off (the 4 step technique is more fully explained by Monica Bruckner, 2016).
Once we are finished staining, we can carry on in the inspection step in studying microbes by taking note of any qualifying or quantifying phenotypes that stand out. Of course, before the “inspection” step, there was the “inoculation” or transfer of the microbe, the “incubation” or growth and “isolation” or separation of any different microbes from the one being investigated. After inspection, we can go on to do “information gathering” or assessing drug sensitivity, DNA sequencing and biochemical tests, and finally using a key to “identify” the microbe, or by sending the sequences through GenBank for analysis. These steps together form the six “i’s” of microbiology. (Talaro and Chess, 2011). Once you have identified the microbe, you can begin the real fun, finding the right primers to isolate a specific protein or gene during PCR, testing the the isolates against any compounds you wish, and possibly publishing your results.
References
American Society for Microbiology. (2015). “Significant Events in Microbiology 1861-1999.”
American Society for Microbiology. Retrieved from https://www.asm.org/index.php
/choma2/71-membership/archives/7852-significant-events-in-microbiology-since-1861
Bruckner, M. (2016). “Basic Cell Staining.” Microbial Life Educational Resources. Retrieved
Talaro, K. and Chess, B. (2011). “Foundations In Microbiology: 8th Edition.” McGraw-Hill.
Ch. 3. Retrieved from http://learning.hccs.edu/faculty/joy.marshall/microbiology-
power-points/chapter-3-lecture-power-point
