Introductory Microbiology

Mesosomes and Cytoplasm

Mesosomes

 
• In some bacteria, particularly in the gram +ve bacteria depending upon growth conditions the membrane appears to be infolded at more than one point. Such infoldings are called mesosomes. The presence of such structures in large numbers have also been found in organisms that have a higher respiratory activity as in the nitrogen fixing bacteria namely Azatobacter during logarithmic growth phases. In photosynthetic bacteria the extent of membrane infolding has been related to pigment content and photosynthetic activity. In sporulating bacteria, the appearance of such infolding (mesosome formation) is a prerequisite for and sporulation

Cytoplasm
The major cytoplasmic contents of bacterial cell include the nucleus, ribosomes, proteins and other water soluble components and reserve material. In most bacteria, extrachromosomal DNA or plasmid DNA is also present. The plasmid DNA is circular and double stranded.