Search results
Results from the WOW.Com Content Network
Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. [1] Historically, most definitions of life postulated that an organism must be composed of one or more cells, [2] but, for some, this is no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. [1] Their defining characteristic is that their cell envelope consists of a thin peptidoglycan cell wall sandwiched between an inner ( cytoplasmic ) membrane and an outer ...
Microbes are important in human culture and health in many ways, serving to ferment foods and treat sewage, and to produce fuel, enzymes, and other bioactive compounds. Microbes are essential tools in biology as model organisms and have been put to use in biological warfare and bioterrorism. Microbes are a vital component of fertile soil.
Bacteria can be classified on the basis of cell structure, cellular metabolism or on differences in cell components, such as DNA, fatty acids, pigments, antigens and quinones. [118] While these schemes allowed the identification and classification of bacterial strains, it was unclear whether these differences represented variation between ...
Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet during Gram staining, resulting in a purple color. Gram-negative bacteria have a thin peptidoglycan layer which does not retain the crystal violet, so when safranin is added during the process, they stain red.
When first introduced by Georg Goldfuss, in 1818, the taxon Protozoa was erected as a class within the Animalia, [3] with the word 'protozoa' meaning "first animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as found in plants and many algae.
Diener initially hypothesized in 1989 that viroids may represent "living relics" from the widely assumed, ancient, and non-cellular RNA world, and others have followed this conjecture. [ 13 ] [ 14 ] Following the discovery of retrozymes , it has been proposed that viroids and other viroid-like elements may derive from this newly found class of ...
A comprehensive study of DNA sequences from multiple human samples inferred the existence of 4,930 species of microbes of which 77% were previously unreported. [33] Health-related findings include a prophage that might be associated with cirrhosis of the liver , [ 27 ] and seven novel sequences from children with type-1 diabetes that have ...