DIFFERENCE BETWEEN GRAM POSITIVE BACTERIA AND GRAM NEGATIVE BACTERIA

TYPES OF BACTERIA

·       A few different criteria are used to classify Bacteria. The organisms can be distinguished by

a)     The nature of their cell walls (Gram positive bacteria and Gram negative bacteria)

b) Their shapes (Coccus, Bacillus, Spirilla, Box, Filamentous, Appentaged and Pleomorphic)

c)     Gaseous requirements or Respiration (Aerobic bacteria and Anaerobic bacteria)

d)     Nutritional pattern (Autotrophic bacteria and Heterotrophic bacteria)

Table – 8.1: Difference between Gram positive bacteria and Gram negative bacteria

S. No	Features	Gram Positive Bacteria	Gram Negative Bacteria
1	Gram staining	Appears in Violet colour	Appears in Pink colour
2	Examples	Staphylococcus, Streptococcus, Lactobacillus, Clostridium and Bacillus.	Neisseria, Escherichia coli, Salmonella, Vibrio, Klebsiella, Rhizobium and Azospirillum
3	Cell wall
	Thickness	15 – 18 nm	7 – 8 nm
	Peptidoglycan	Thick (Multilayered)	Thin (Single layered)
	Teichoic acids	Present	Absent
	Periplasmic space	Absent	Present
	Outer membrane	Absent	Present
	Lipopolysaccharides	No	High
	Lipid & Lipoproteins	Low (Only in Acid fast bacteria have lipid linked to Peptidoglycan)	High (because of the presence of Outer membrane)
	Porins	Absent	Present
	Cell wall disruption by Lysozymes	High (After digestion of peptidoglycan layer, Gram positive bacteria become Protoplast)	Low (After digestion of peptidoglycan layer, Gram   negative bacteria become Spheroplast)
	Rigidity and Elasticity	High rigid & Less elastic	Less rigid & High elastic
4	Mesosomes	More prominent	Less prominent
5	Endospores	Produced during unfavorable conditions	Not produced
6	Flagella structure	2 rings in Basal body	4 rings in Basal body
7	Toxins produced	Produce Exotoxins	Produce Endotoxins
8	Pathogenic nature	Very few are pathogenic	Most are pathogenic
9	Nutritional requirement	Complex	Simple
10	Isoelectric range pH	2.5 to 4.0	4.5 to 5.5
11	Susceptibility to Penicillin and Sulfonamide	High	Low
12	Susceptibility to Streptomycin, Chloramphenicol and Tetracycline	Low	High
13	Susceptibility to Detergents	High	Low
14	Inhibition by Basic dyes	High	Low
15	Resistance to Physical disruption	High	Low
16	Resistance to Sodium Azide (Bacteriostatic)	High	Low
17	Resistance to Drying	High	Low