Bacterial Cytoplasm

| Home | | Pharmaceutical Microbiology |

Chapter: Pharmaceutical Microbiology : Structure and Function of Bacterial Cells

Based upon various intensive and extensive investigations carried out on the bacterial cell, one may observe that the major cytoplasmic contents of it essentially include not only the nucleus but also ribosomes, proteins, water-soluble components, and reserve material.


Bacterial Cytoplasm

 

Based upon various intensive and extensive investigations carried out on the bacterial cell, one may observe that the major cytoplasmic contents of it essentially include not only the nucleus but also ribosomes, proteins, water-soluble components, and reserve material. It has also been observed that a plethora of bacteria do contain extrachromosomal DNA i.e., DNA that are not connected to the chromosomes.

 

It has also been revealed that the ‘bacterial nucleus’ is not duly enclosed in a well-defined mem-branous structure, but at the same time comprises of the genetic material of the bacterial cell. Interest ingly, several altogether sophisticated meticulous and methodical investigations pertaining to the actual status/content(s) of the bacterial nucleus reveal amply that :

 

(a) Electron microscopy : Electron micrographs of the bacterial nucleus under investigation evidently depict it as a region very tightly and intimately packed with fibrillar DNA i.e., consisting of very small filamentous structure.

 

(b) Cytological, biochemical, physical, and genetic investigations : Such investigations with respect to a large cross-section of bacterial species revealed that the ‘bacterial nucleus’ essentially contains a distinct singular molecule of definite circular shape, and having a double-stranded DNA.

 

The genome size of DNA i.e., the complete set of chromosomes, and thus the entire genetic information present in a cell, obtained painstakingly from a variety of bacterial species has been deter-mined and recorded in Table 2.9 below :


 

Specifications of E. coliThe size of DNA in E. coli together with certain other specifications are as given below :

 

Average length : Approx. 1000 μm

Base pairs : 5 × 103 kilo base pairs

Molecular weight : 2.5 × 109 Daltons (± 0.5 × 109)

 

The ensuing DNA happens to be a highly charged molecule found to be dissociated with any basic proteins as could be observed in higher organisms.

 

Neutralization of charge is duly caused either by polyamines e.g., spermine, spermidine, or by bivalent cations e.g., Mg2+, Ca2+.

 

Plasmid DNA : Besides, the apparent and distinct presence of the bacterial ‘nuclear DNA’, they invariably contain extrachromosomal* DNA termed as plasmid DNA that replicates autonomously. It has been duly observed these plasmid DNAs exhibit different specific features, such as :

·        confer on the bacterial cell,

·        drug resistance,

·        ability to generate bacteriocins i.e., proteinaceous toxins.

·        ability to catabolize uncommon organic chemical entities (viz., in Pseudomonas).

Nevertheless, the actual size of plasmid DNA usually found in these specific structures may be nearly 1/10th or even less in comparison to that invariably found in the bacterial nucleus ; however, the exact number of copies may change from one to several. Besides, these structures are not enclosed in a membrane structure. Importantly, the plasmid DNA is mostly circular in shape and double stranded in its appearance.

 

Copyright © 2019, 2020 pharmacy180.com; Developed by Therithal info.