How is bacteria identified

Each pathogenic species has a characteristic spectrum of interactions with its human hosts. Conditionally, pathogenic bacteria are only pathogenic under certain conditions; such as a wound that allows for entry into the blood, or a decrease in immune function. Bacterial infections can also be classified by location in the body, for example, the vagina, lungs, skin, spinal cord and brain, and urinary tract.

When identifying bacteria in the laboratory, the following chatacteristics are used: Gram staining, shape, presence of a capsule, bonding tendency singly or in pairs , motility, respiration, growth medium, and whether it is intra- or extracellular. Culture techniques are designed to grow and identify particular bacteria, while restricting the growth of the others in the sample. Often these techniques are designed for specific specimens: for example, a sputum sample will be treated to identify organisms that cause pneumonia.

Once a pathogenic organism has been isolated, it can be further characterised by its morphology, growth patterns aerobic or anaerobic , patterns of hemolysis, and staining.

Similar to the classification systems used for cellular organisms, virus classification is the subject of ongoing debate due to their pseudo-living nature. Essentially, they are non-living particles with some chemical characteristics similar to those of life; thus, they do not fit neatly into an established biological classification system.

Currently there are two main schemes used for the classification of viruses: 1 the International Committee on Taxonomy of Viruses ICTV system; and 2 the Baltimore classification system, which places viruses into one of seven groups.

To date, six orders have been established by the ICTV:. Baltimore classification is a system that places viruses into one of seven groups depending on a combination of:. Other classifications are determined by the disease caused by the virus or its morphology, neither of which is satisfactory as different viruses can either cause the same disease or look very similar. In addition, viral structures are often difficult to determine under the microscope. Classifying viruses according to their genome means that those in a given category will all behave in a similar fashion, offering some indication of how to proceed with further research.

Other organisms invariably cause disease in humans, such as obligate intracellular parasites that are able to grow and reproduce only within the cells of other organisms.

In ecology, microorganisms are classified by the type of habitat they require, or trophic level, energy source and carbon source. Biologists have found that microbial life has an amazing flexibility for surviving in extreme environments that would be completely inhospitable to complex organisms.

An extremophile is an organism that thrives in physically or geochemically extreme conditions, detrimental to most life on Earth. Most known extremophiles are microbes. The domain Archaea contains renowned examples, but extremophiles are present in numerous and diverse genetic lineages of both bacteria and archaeans. In contrast, organisms that live in more moderate environments may be termed mesophiles or neutrophiles.

There are many different classes of extremophiles, each corresponding to the way its environmental niche differs from mesophilic conditions. Many extremophiles fall under multiple categories and are termed polyextremophiles. Some examples of types of extremophiles:. The nutritional modes of an organism : A flowchart to determine if a species is autotroph, heterotroph, or a subtype. Differing morphology in different Herpes viruses : Various viruses from the Herpesviridae family seen using an electron micrograph.

Privacy Policy. Skip to main content. Microbial Evolution, Phylogeny, and Diversity. Search for:. Methods of Classifying and Identifying Microorganisms. Phenotypic Analysis Microorganisms can be classified on the basis of cell structure, cellular metabolism, or on differences in cell components.

Learning Objectives Distinguish between phenotypic characteristics for Bacteria, Archaea and Eukaryotes. Key Takeaways Key Points The relationship between the three domains Bacteria, Archaea, and Eukaryota is of central importance for understanding the origin of life. Most of the metabolic pathways are common between Archaea and Bacteria, while most genes involved in genome expression are common between Archaea and Eukarya.

They include bacteria, fungi, algae, and protozoa; microscopic plants, and animals. Yersinia pestis is the causative agent of bubonic plague. So, how do we go about identifying microbes?

Traditional methods rely on phenotypic identification using staining, culturing, and simple biochemical tests. Nowadays, more powerful molecular, immunological, and biochemical analytical methods complement and sometimes replace traditional methods. Macroscopic features encompass the overall appearance of a microorganism, including its shape, size, color, and smell i.

Stains enable easier visualization under a microscope. Cytology microscopes have specific requirements to ensure clear differentiation between stained cells. Gram staining is often the go-to test in bacterial identification. This purple stain, based on the crystal violet dye, is named after the Danish bacteriologist Hans Christian Gram, who developed it.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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