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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]
Veillonella are Gram-negative bacteria (Gram stain pink) anaerobic cocci, unlike most Bacillota, which are Gram-positive bacteria. [1] This bacterium is well known for its lactate fermenting abilities. It is a normal bacterium in the intestines and oral mucosa of mammals.
Anaerobic bacteria usually do not possess catalase, but some can generate superoxide dismutase which protects them from oxygen. The clinically important anaerobes in decreasing frequency are: [2] 1. Six genera of Gram-negative rods (Bacteroides, Prevotella, Porphyromonas, Fusobacterium, Bilophila and Sutterella spp.); 2.
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.
The cocci shaped Thiomargarita can join together to create chains of 4-20 cells, while the bacillus shaped Thiomargarita can form chains of more than 50 cells. [25] These chains are not linked together by filaments, but connected by a mucus sheath. [6] Each cell appears reflective and white as a result of their sulfur content. [26]
Examples of obligately anaerobic bacterial genera include Actinomyces, Bacteroides, Clostridium, Fusobacterium, Peptostreptococcus, Porphyromonas, Prevotella, Propionibacterium, and Veillonella. Clostridium species are endospore-forming bacteria, and can survive in atmospheric concentrations of oxygen in this dormant form. The remaining ...
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 ...
E. coli is a gram-negative, facultative anaerobe, nonsporulating coliform bacterium. [18] Cells are typically rod-shaped, and are about 2.0 μm long and 0.25–1.0 μm in diameter, with a cell volume of 0.6–0.7 μm 3. [19] [20] [21] E. coli stains gram-negative because its cell wall is composed of a thin peptidoglycan layer and an outer membrane.