Koch Postulates
Koch Postulates - Related Videos
02:43
Basic Postulates of Kinetic Molecular Theory: Particle Size, Energy, and Collision
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2020
The ideal-gas equation, which is empirical, describes the behavior of gases by establishing relationships between their macroscopic properties. For example, Charles’ law states that volume and temperature are directly related. Gases, therefore, expand when heated at constant pressure. Although gas laws explain how the macroscopic properties change relative to one another, it does not explain the rationale behind it. The kinetic molecular theory is a microscopic model that helps understand what...
02:59
The Atomic Theory of Matter
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2020
The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter was composed of small, finite particles that they called atomos, meaning “indivisible.” Later, Aristotle and others came to the conclusion that matter consisted of various combinations of the four “elements” — fire, earth, air, and water — and could be infinitely divided. Interestingly, these philosophers thought about atoms and “elements” as...
12:47
A Technique to Screen American Beech for Resistance to the Beech Scale Insect (Cryptococcus fagisuga Lind.)
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Cited by 8 •
2014
Beech bark disease is initiated by feeding activities of the beech scale insect that create fungal entry points in the bark. Trees that are resistant to the scale insect are also disease resistant. Here we present the protocol we have developed to screen individual beech trees for beech scale resistance.
07:05
Measuring Enzymatic Activity of Neurodevelopmental Disorder-Associated Deubiquitylating Enzymes via an In Vitro Ubiquitin Chain Cleavage Assay
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2024
This protocol explains how to measure the effect of genetic variation associated with neurodevelopmental disorders on deubiquitylating enzyme activity by combining recombinant protein purification with ubiquitin chain cleavage assays.
00:48
Optimal Foraging
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2019
How animals obtain and eat their food is called foraging behavior. Foraging can include searching for plants and hunting for prey and depends on the species and environment. Optimal foraging theory states that natural selection favors foraging strategies that balance the benefits of a particular food, such as energy and nutrients, with the costs of obtaining it, such as energy expenditure and the risk of predation. Optimal foraging maximizes benefits while minimizing costs. For the Crows
FAQs
The framework links four observations into a causal chain rather than treating simple coexistence as proof. The microorganism must be associated with diseased hosts, separated from other organisms by pure culture, connected to disease in a healthy susceptible host, and recovered afterward. Agreement across these stages strengthens the conclusion that the organism is responsible for the disease.
Pure culture separates the suspected pathogen from other microorganisms present in diseased tissue. Without that separation, a later disease response could not be confidently attributed to one organism. This requirement turns an initial association into a more controlled test of causation and supports clearer pathogen identification in infectious-disease investigations.
A healthy susceptible host provides a clearer test of whether exposure to the isolated microorganism can reproduce the disease. Existing illness could obscure the organism's effect, while resistance could prevent disease even when the organism is involved. This condition helps connect the isolated microorganism with the characteristic disease outcome.
The classical criteria do not fit every infectious disease. Some organisms cannot be cultured, and certain diseases have multiple causes rather than one responsible microorganism. Asymptomatic carriers also complicate the expectation that an organism will be found only in diseased hosts. These limitations prevent the criteria from serving as a universal test in every case.
After disease is reproduced in a healthy susceptible host, investigators recover the same microorganism from that host. This final comparison links the experimental illness back to the organism originally isolated from diseased tissue. It helps exclude the possibility that the observed disease resulted from an unrelated microorganism or condition introduced during the investigation.
They provide a structured basis for pathogen identification, disease diagnosis, and experimental studies of host-microbe relationships. By requiring observations at several stages, the criteria help researchers evaluate whether a particular microorganism is associated with a specific disease in a biologically meaningful way. Their logic has shaped medical microbiology and infectious-disease research.
Molecular and epidemiological approaches can provide additional evidence when culture-based testing is not feasible or when disease causation is complex. Molecular methods address situations involving organisms that cannot be cultured, while epidemiological approaches help evaluate patterns involving multiple causes or asymptomatic carriers. Together, these approaches extend investigation beyond the classical framework.