Question

What are some examples of gram negative bacteria?

Answer 1

Hint: Bacteria are monera, prokaryotic microorganisms that are basically unicellular, devoid of chlorophyll a, possess nucleoid attached to mesosome, and food reserve in the form of glycogen. They were first seen by Dutch merchant and amateur microscopist Leeuwenhoek (1676) in stored rainwater and tartar scraped from teeth. He named them animalcules (small animals). Linnaeus (1758) called them vermes. The term bacteria was given by Ehrenberg in 1828.

Complete answer:
Gram staining: Christian Gram (1884) developed a technique of staining bacteria called Gram staining. Depending upon reaction to Gram staining, bacteria have been divided into two groups, Gram positive and Gram negative. A bacterial smear is heated on a glass slide. The latter is dipped in a solution of crystal violet for one minute. All types of bacteria pick up a purple colouration. The stain is fixed by dipping the slide in 0.5% iodine solution for one minute. The slide is now kept in a polar organic solvent like alcohol for 10-30 seconds. Some bacteria retain a blue or purple stain. They are called Gram positive. Those lose the stain in organic solvent called Gram negative. The slide is counter-stained with safranin for 20-30 seconds. Gram negative bacteria pick up the pink counter-stain while Gram positive bacteria come to have both purple and pink stains. The difference between Gram +ve and Gram -ve bacteria. The difference between gram positive and gram negative bacteria is due to the difference in lipid content of their walls. In Gram +ve bacteria the wall has little lipid Content. Therefore, little stain leaks in organic solvent. In Gram -ve bacteria the Wall has high lipid content that dissolves in organic solvent taking out the stain alongwith.
Gram Positive Bacteria. Pneumococcus, Streptococcus, Clostridium. Mycobacterium, Streptomyces.
Gram Negative Bacteria. Salmonella, Pseudomonas, Escherichia, Haemophilus, Helicobacter, Vibrio, Rhizobium, Bordetella pertussis, Treponema pallidum, Bordetella recurrentis, Neisseria gonorrhoeae, Neisseria meningitidis, Gardnerella vaginalis.

Note:
1. Bacteria are prokaryotic microorganisms.
2. They are basically unicellular.
3. The surface is covered by a thin or thick layer of mucilage.
4. A wall surrounds each cell.
5. Cell wall contains peptidoglycan. It is formed of N-acetyl glucosamine. N-acetyl muramic acid and small peptides.
6. An organised nucleus is absent. DNA is one double-stranded molecule which is folded to form a nearly compact structure called nucleoid.
7. Extrachromosomal self replicating DNA segments called plasmids occur in many.
8. Cytoplasmic streaming is absent.
9. Ribosomes are cytoplasmic and 70 S in nature.
10. Mitochondria, plastids, Golgi apparatus, E.R., and other membrane covered cell organelles are absent.