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Violet-stained gram-positive cocci and pink-stained gram-negative bacilli. In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.
Gram staining differentiates bacteria by the chemical and physical properties of their cell walls. Gram-positive cells have a thick layer of peptidoglycan in the cell wall that retains the primary stain, crystal violet. Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol.
In such stained preparations, it may appear either as round cells with Gram-positive granular inclusions impressed upon a pale lavender cytoplasmic background or as Gram-negative lipoid bodies. [9] When grown as a yeast, C. neoformans has a prominent capsule composed mostly of polysaccharides.
Examples of gram-negative diplococci are Neisseria spp. and Moraxella catarrhalis. Examples of gram-positive diplococci are Streptococcus pneumoniae and Enterococcus spp. [10] [11] Presumably, diplococcus has been implicated in encephalitis lethargica. [12] The genus Neisseria belongs to the family Neisseriaceae.
Escherichia coli (E. coli), common Gram-negative gut bacterium widely used in molecular genetics. Main lab strain is 'K-12'. Bacillus subtilis, endospore forming Gram-positive bacterium. Main lab strain is '168'. Caulobacter crescentus, bacterium that divides into two distinct cells used to study cellular differentiation.
Fungal yeast forms are inconsistently stained with Acid-fast stain which is considered a narrow spectrum stain for fungi. [21] In a study on acid-fastness of fungi, [ 22 ] 60% of blastomyces and 47% of histoplasma showed positive cytoplasmic staining of the yeast-like cells, and Cryptococcus or candida did not stain, and very rare staining was ...
Saccharomyces is a genus of fungi that includes many species of yeasts. Saccharomyces is from Greek σάκχαρον (sugar) and μύκης (fungus) and means sugar fungus.Many members of this genus are considered very important in food production where they are known as brewer's yeast, baker's yeast and sourdough starter among others.
Lactobacillus is a genus of gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. [2] [3] Until 2020, the genus Lactobacillus comprised over 260 phylogenetically, ecologically, and metabolically diverse species; a taxonomic revision of the genus assigned lactobacilli to 25 genera (see § Taxonomy below).