There is vast variety of bacteria in and around us. Bacteria are classified into various groups based on genetic, morphological, and biochemical characteristics.
Taxonomic diversity includes proteobacteria, firmicutes, actinobacteria and bacteroidetes. All of these play a role in the environment or your body. Some, like proteobacteria, are pathogens such as E. Coli. Others, like bacteroidetes, are the helpful bacterium found in the human gut. Actinobacteria are found in soil and known for their antibiotic production.
These bacteria inhabit a wide range of environments, from extreme conditions (hot springs, deep-sea vents) to more common habitats (soil, water, and human microbiomes). Their roles vary significantly. Decomposers break down organic matter. Symbionts form beneficial relationships between plants and animals. For example, there are nitrogen-fixing bacteria in legumes. There are bacteria in our gut that help us digest specific food groups. Bacteria can be exceedingly helpful. Some bacteria, though, can be just the opposite. Proteobacteria, which we mentioned, belongs to the pathogen group. Pathogens cause disease in humans, animals, and plants. These bacteria thrive in different conditions, doing different things, through their metabolic capabilities. Some can photosynthesize, respire anaerobically, or fix nitrogen. This functional diversity is part of what makes bacteria unique from each other.
Bacterial diversity is essential for human health, the environment, and biotechnology. But will all these bacteria out there, how do we tell them apart? How do we sort them?
Morphology is one of the easiest ways to sort bacteria. While you can’t see them with the naked eye, with the use of a microscope we can easily find the shape, arrangement, and size of a bacteria. They can cocci (spherical), bacilli (rod-shaped), or spirilla (spiral). Another way to tell bacteria apart are by their peptidoglycan layer in their cell walls. We do this through the process of gram staining. This gram positivity or negativity can also give us insight into their antibiotic susceptibility.
Biochemical tests are another great way to characterize bacteria. These tests assess metabolic activities, such as fermentation of sugars, production of gas, or enzyme activity (e.g., catalase, oxidase tests). Similarly, you can use molecular techniques like PCR (Polymerase Chain Reaction) and sequencing allow for identification based on genetic material. This can be highly specific and sensitive.
Culture characteristics can also be useful in separating bacteria. Some media allow certain bacteria to grow while inhibiting others.
Antibiotic resistance tends to form patterns in bacteria species. By exposing bacteria to others, they may display antibiotic resistance or production which can help further separate them.
To get a little more specific, you can use serology. It’s the use of antibodies to detect specific antigens on the bacterial surface. This can help differentiate strains. Fatty acid analysis can be another in-depth look. Profiling fatty acids in the bacterial membrane can provide distinct signatures for different species.
By combining these methods, microbiologists can accurately identify and differentiate bacterial species. Bacteria are so diverse and abundant that it is critical to be able to accurately tell them apart in many ways. Understanding this diversity can lead to insights in medicine, agriculture, and environmental science.
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