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Structure b represents diplococcus bacteria. Diplococci are pairs of cocci. 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]
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 ...
Helicobacter is a genus of gram-negative bacteria possessing a characteristic helical shape. They were initially considered to be members of the genus Campylobacter, but in 1989, Goodwin et al. published sufficient reasons to justify the new genus name Helicobacter. [2] The genus Helicobacter contains about 35 species. [3] [4] [5]
A spirochaete (/ ˈ s p aɪ r oʊ ˌ k iː t /) [4] or spirochete is a member of the phylum Spirochaetota (also called Spirochaetes [5] / ˌ s p aɪ r oʊ ˈ k iː t iː z /), which contains distinctive diderm (double-membrane) Gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or spiraled, hence the name) cells ...
Helicobacter pylori is a species of gram-negative bacteria in the Helicobacter genus. [23] About half the world's population is infected with H. pylori but only a few strains are pathogenic. H pylori is a helical bacterium having a predominantly helical shape, also often described as having a spiral or S shape.
Gram-negative and mycobacteria have an inner and outer bacteria membrane. As a phospholipid bilayer , the lipid portion of the bacterial outer membrane is impermeable to charged molecules. However, channels called porins are present in the outer membrane that allow for passive transport of many ions , sugars and amino acids across the outer ...
Some bacteria have cell wall structures that are neither classically Gram-positive or Gram-negative. This includes clinically important bacteria such as mycobacteria which have a thick peptidoglycan cell wall like a Gram-positive bacterium, but also a second outer layer of lipids.
A well accepted example of pleomorphism is Helicobacter pylori, which exists as both a helix-shaped form (classified as a curved rod) and a coccoid form. [7] Legionella pneumophila, the species of intracellular bacteria parasite responsible for Legionnaire's disease, has been seen to differentiate within a developmentally diverse network. [8]