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Bacteria display a large diversity of cell morphologies and arrangements. Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archaea).
Antonie van Leeuwenhoek (1632–1723), the first microbiologist and the first person to observe bacteria using a microscope in 1676. Bacteria were first observed by the Dutch microscopist Antonie van Leeuwenhoek in 1676, using a single-lens microscope of his own design. He then published his observations in a series of letters to the Royal ...
Bacteria and archaea are almost always microscopic, while a number of eukaryotes are also microscopic, including most protists, some fungi, as well as some micro-animals and plants. Viruses are generally regarded as not living and therefore not considered to be microorganisms, although a subfield of microbiology is virology , the study of viruses.
The bacterial DNA is not packaged using histones to form chromatin as in eukaryotes but instead exists as a highly compact supercoiled structure, the precise nature of which remains unclear. [6] Most bacterial chromosomes are circular, although some examples of linear chromosomes exist (e.g. Borrelia burgdorferi). Usually, a single bacterial ...
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 ...
Bacillus (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum Bacillota, with 266 named species.The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural Bacilli is the name of the class of bacteria to which this genus belongs.
Gram stain of cells from the vagina (the same magnification) with normal bacterial flora (top) and the bacteria that cause vaginosis (bottom). A variety of diagnosis techniques are currently available for identifying Gardnerella vaginalis such as the OSOM BV Blue assay, FemExam cards and nucleic acid amplification tests (NAATs), resulting in the determination of ongoing BV.
This bacteria often occur in large numbers within the lesions of lepromatous leprosy and are usually grouped together as a palisade. [6] By optical microscopy of host cells, Mycobacterium leprae can be found singly or in clumps referred to as "globi", the bacilli can be straight or slightly curved, with a length ranging from 1–8 μm and a ...