Bubonic Plague “Black Death” has a very rapid transition from asymptomatic- fatal sepsis and bursting lymph nodes.
An organism refers to a living thing that has an organized structure, can react to stimuli, reproduce, grow, adapt, and maintain homeostasis.
Organisms can be any animal, plant, fungus, protist, bacterium, or archaeon on earth.
Organisms may be classified based upon the number of cells that make it up, with two major groups being the single-celled (e.g. bacteria, archaea, protists) and the multicellular (animals and plants).
Organisms with a well-defined nucleus are referred to as eukaryotes, whereas those without are called prokaryotes.
Trillions of microbial species live within us, known as the microbiome, which is essential for normal development, physiology and defence.
The microbiome is important in pathology and scientists aim to elucidate how the composition and functions of the human microbiota influence the initiation and progression of important human diseases, such as diabetes and cancer.
The microbiome is a dynamic system that alters over the course of a person’s life, impacted by environmental factors and lifestyle habits such as personal hygiene, diet, who they interact with and where they live.
Antibiotics consumption also affects the microbiome.
The gut microbiome has a beneficial role during normal homeostasis, modulating the host’s immune system and influencing host development and physiology, including organ development and morphogenesis, and host metabolism.
Hawaiian bobtail squid and the marine bacterium Vibrio fischeri form a symbiotic relationship to produce light, the host uses as camouflage in a nocturnal behaviour called counterillumination that disrupts the host’s silhouette.
Hawaiian bobtail squid development is dependent upon bacteria, with Vibrio fischeri being harvested and cultured in specific crypts within the squid.
The microbiomes of deep-sea hydrothermal vents are diverse and contain novel species, reflecting the diversity of life on earth.
Over the last 3.7 billion years, living organisms on the Earth have diversified and adapted to almost every environment imaginable.
All living organisms share similarities, such as replication and the replicator molecule being DNA.
All living organisms convert the information stored in DNA into products used to build cellular machinery from fats, proteins, and carbohydrates.
Biological diversity, also known as biodiversity, refers to the variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur.
Biological diversity is constantly changing, being increased by new genetic variation and reduced by extinction and habitat degradation.
Tuberculosis translocates to the lower respiratory tract, where it is engulfed by alveolar macrophages.
Alveolar macrophages internalize the bacteria by receptor-mediated phagocytosis, which fuse with lysosomes.
Lysosomes are vesicles within cells that have a low pH to degrade phagocytosed material.
Normally, bacteria engulfed by phagocytosis are degraded by the lysosome.
Tuberculosis actively blocks phagosome fusion with the lysosome, ensuring its survival within alveolar macrophages.
Tuberculosis accesses the parenchyma by recruiting cells to the site of infection generating a multicellular host response called a granuloma.
The granuloma is involved in both the control of the infection and the persistence of the pathogen.
Gonorrhoea is caused by Neisseria gonorrhoeae, a diplococcal bacterium that is mainly colonized in the genital mucosa but can also colonize the ocular, nasopharyngeal and anal mucosa.
Maternal transmission to children during birth can lead to neonatal blindness.
Untreated N. gonorrhoeae infection can lead to disseminated gonococcal infection, giving rise to infectious arthritis and endocarditis.
Vibrio cholerae, the aetiological agent of cholera, is a Gram-negative rod that colonizes the small intestine for 12 to 72 hours before symptoms appear.
Cholera often begins with stomach cramps and vomiting followed by diarrhoea.
Cholera toxin is a protein exotoxin that consists of 1 A subunit associated with 5 B subunits.
The B subunit pentamer binds to the ganglioside GM1 on eukaryotic cells.
The A subunit is translocated to the inside of the cell and enzymatically activates adenylate cyclase, raising intracellular cAMP.
Intracellular cAMP leads to chloride secretion through the apical chloride channel and water moving across membrane, resulting in secretory watery diarrhoea, also known as rice water stool.
Plague is a vector-borne illness transmitted by fleas to a variety of rodents- reservoirs for the disease.
The etiological agent of plague is the Gram negative bacterium Yersinia pestis.
Plague has impacted the history of humankind through several pandemics.
In the 21st century, plague is present in Asia, Africa and America.
Species diversity: the number of different species in a particular ecosystem or on Earth.
Ecosystem diversity: biologists look at the many types of functional units formed by living communities interacting with their environments.