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Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. They are pigmented with bacteriochlorophyll a or b , together with various carotenoids , which give them colours ranging between purple, red, brown, and orange.
Purple-stained gram-positive (left) and pink-stained gram-negative (right) Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan (50–90% of cell envelope), and as a result are stained purple by crystal violet, whereas gram-negative bacteria have a thinner layer (10% of cell envelope), so do not retain the purple stain ...
Gram-positive bacteria have a thick layer of peptidoglycan within the cell wall, and Gram-negative bacteria have a thin layer of peptidoglycan. Gram-positive bacteria take up the crystal violet stain used in the test, and then appear to be purple-coloured when seen through an optical microscope.
Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. Currently, they are considered the predominant phylum within the realm of bacteria. They are naturally found as pathogenic and free-living (non-parasitic) genera.
The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic , and are often found in stratified water environments including hot springs , stagnant water bodies, as well as microbial mats in intertidal zones.
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.
Rhodopseudomonas palustris is a rod-shaped, Gram-negative purple nonsulfur bacterium, notable for its ability to switch between four different modes of metabolism. [2] R. palustris is found extensively in nature, and has been isolated from swine waste lagoons, earthworm droppings, marine coastal sediments, and pond water.
Indole-Negative Bacteria Bacteria which give negative results for the indole test include: Actinobacillus spp., Aeromonas salmonicida , Alcaligenes sp., most Bacillus sp., Bordetella sp., Enterobacter sp., most Haemophilus sp., most Klebsiella sp., Neisseria sp., Mannheimia haemolytica , Pasteurella ureae , Proteus mirabilis , P. penneri ...
Characterizes bacteria in one of two groups, Gram positive or Gram negative Gram positive appears purple in color Grams negative appears pink in color 4 Acid fast (Ziehl-Neelsen technique) Film stained with hot Z.N.C.F. decolourized (acid-alcohol) and counter stain with methylene blue
In microscopy, negative staining is an established method, often used in diagnostic microscopy, for contrasting a thin specimen with an optically opaque fluid. In this technique, the background is stained, leaving the actual specimen untouched, and thus visible.