Is the gram reaction due to the outer membrane?

What are the key differences between gram-negative and gram-positive bacteria?

Gram-negative bacteria have a thin peptidoglycan layer in their cell wall and an outer membrane, while gram-positive bacteria have a thick peptidoglycan layer but lack an outer membrane. Gram-negative bacteria also have lipopolysaccharides in their outer membrane, which gram-positive bacteria do not have. Additionally, gram-negative bacteria are typically more resistant to antibiotics due to the presence of the outer membrane.

Are there endospores in pseudomonas aeruginosa gram staining?

Pseudomonas aeruginosa does not form endospores. In Gram staining, it typically stains gram-negative due to its thin peptidoglycan layer and outer lipid membrane.

How is the bacteria in genus grouped in terms of Gram classification?

They are considered Gram positive due to their lack of an outer cell membrane even though they do not retain the crystal violet stain.

What is the gram reaction of non-acid- fast bacteria?

Non-acid-fast bacteria typically have a Gram reaction of either Gram-positive or Gram-negative. Gram-positive bacteria retain the crystal violet stain and appear purple under a microscope due to their thick peptidoglycan cell wall. In contrast, Gram-negative bacteria do not retain the crystal violet stain; they take up the counterstain (usually safranin) and appear pink due to their thinner peptidoglycan layer and outer membrane. The distinction is important for identifying and treating bacterial infections.

Why is EColi a gram negative bacteria?

E.coli is gram -ve and should stain pink in gram staining. The reason for its blue appearance is due to the over absorption of dye which can be due to either prolonged contact of dye or delay in washing or may be the concentration of soloution of dye is high

What is the difference in color between gram positive and gram negative bacteria?

Gram positive bacteria appear purple or blue when stained with the Gram stain, while gram negative bacteria appear pink or red. This color difference is due to the thickness of the cell wall and the presence of an outer membrane in gram negative bacteria.

What shape are gram negative bacteria?

Gram negative bacteria are typically rod-shaped (bacilli) or corkscrew-shaped (spirochetes). They have a double cell membrane composed of an inner and outer membrane, which contributes to their staining properties in the Gram staining technique.

Differences between gram positive and negative bacteria in table?

Best Answer By: Mohamed Ahmed A. XeriyeBiology Teacherthey are different so many aspects among :1. the peptidoglycan layer is absent from grma-ve bacteria while its present in gram +ve bacetria.2. techoic acids are present in gram - positive, and absent from gram - negative bacteria3. the outer membrane is absent from gram - positive, and present in gram - negativethere are so many differences between them.

Compare gram-positive bacteria with gram-negative bacteria?

Gram-positive bacteria have a thick layer of peptidoglycan in their cell wall that retains the crystal violet stain during Gram staining, making them appear purple. In contrast, gram-negative bacteria have a thinner layer of peptidoglycan and an outer membrane that can be disrupted during the staining process, causing them to appear pink. Gram-negative bacteria are generally more resistant to antibiotics due to the presence of this outer membrane.

Gram negative bacteria are much more resistant to penicillin because?

Gram-negative bacteria are more resistant to penicillin due to the presence of an outer membrane that acts as a barrier, preventing the antibiotic from reaching its target (peptidoglycan layer). Additionally, gram-negative bacteria possess enzymes called beta-lactamases that can break down penicillin and render it ineffective. These mechanisms make it harder for penicillin to kill gram-negative bacteria compared to gram-positive bacteria.

What is the appearance of Gram Negative bacteria after alcohol?

Gram Negative bacteria will appear pink or red after alcohol treatment in the Gram staining procedure due to the decolorization of the crystal violet dye. This is because the outer membrane of Gram Negative bacteria is disrupted by the alcohol, allowing the dye to be washed away.

What is the difference between gram positive and gram negative cell wall?

there is only difference in gram positive and negative is of cell wall as :The Gram positive cell wallThe Gram positive cell wall is characterised by the presence of a very thick peptidoglycan layer, which is responsible for the retention of the crystal violet dyes during the Gram staining procedure. It is found exclusively in organisms belonging to the Actinobacteria (or high %G+C Gram positive organisms) and the Firmicutes (or low %G+C Gram positive organisms). Bacteria within the Deinococcus-Thermus group may also exhibit Gram positive staining behaviour but contain some cell wall structures typical of Gram negative organisms. Imbedded in the Gram positive cell wall are polyalcohols called teichoic acids, some of which are lipid-linked to form lipoteichoic acids. Because lipoteichoic acids are covalently linked to lipids within the cytoplasmic membrane they are responsible for linking the peptidoglycan to the cytoplasmic membrane. Teichoic acids give the Gram positive cell wall an overall negative charge due to the presence of phosphodiester bonds between teichoic acid monomers.The Gram negative cell wallUnlike the Gram positive cell wall, the Gram negative cell wall contains a thin peptidoglycan layer adjacent to the cytoplasmic membrane, which is responsible for the cell wall's inability to retain the crystal violet stain upon decolourisation with ethanol during Gram staining. In addition to the peptidoglycan layer the Gram negative cell wall also contains an additional outer membrane composed by phospholipids and lipopolysaccharides which face into the external environment. The highly charged nature of lipopolysaccharides confer an overall negative charge to the Gram negative cell wall. The chemical structure of the outer membrane lipopolysaccharides is often unique to specific bacterial strains (i.e. sub-species) and is responsible for many of the antigenic properties of these strains.As a phospholipid bilayer, the lipid portion of the outer membrane is largely impermeable to all 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 membrane. These molecules are therefore present in the periplasm, the region between the plasma membrane and outer membrane. The periplasm contains the peptidoglycan layer and many proteins responsible for substrate binding or hydrolysis and reception of extracellular signals. The periplasm is thought to exist as a gel-like state rather than a liquid due to the high concentration of proteins and peptidoglycan found within it. Because of its location between the cytoplasmic and outer membranes, signals received and substrates bound are available to be transported across the cytoplasmic membrane using transport and signalling proteins imbedded there.