Nucleus and ribosomes

The nucleus contains the DNA of the microbe. In eukaryotic microbes the nucleus usually contains more than one chromosome, in which the DNA is protected by histone proteins. In diploid organisms these chromosomes are paired. However, in some protista there are two distinct types of nuclei within one cell, and they may be polyploid. The larger of the two nuclei is termed a macronucleus and this nucleus is associated with cellular function. The smaller micronucleus functions in controlling reproduction.

The nucleus is surrounded by the nuclear membrane, a double membrane that is perforated by many pores where the two membranes fuse. It is via these pores that the nucleus remains in constant control of the rest of the cell machinery via mRNA and ribosomes. In places the nuclear membrane is also continuous with the endoplasmic reticulum. Within the nucleus is the nucleolus, an RNA-rich area where rRNA is synthesized. Eukaryotic ribosomes are essentially very similar to those of prokaryotes but they are slightly larger, their two subunits are of 60S and 40S, making a dimer of 80S. Their function is the same as that of prokaryotes.