Final answer:
Bacterial and archaeal genomes vary in size, with some as small as approximately 580,000 base pairs in organisms like Mycoplasma genitalium, while others like E.coli have about 4.6 million base pairs and roughly 4,400 genes.
Step-by-step explanation:
The number of nucleotides and genes present in most bacterial and archaeal genomes varies considerably. For instance, some bacterial genomes such as Mycoplasma genitalium are exceptionally compact with only about 580,000 base pairs, while others like Escherichia coli (E.coli) have larger genomes comprising about 4.6 million base pairs.
The gene count differs as well, with small bacteria genomes encoding for fewer genes due to their reliance on host cells for certain functions, while E.coli has approximately 4,400 genes.
Bacterial genomes tend to be more streamlined compared to eukaryotic genomes like humans, which have about 3 billion base pairs per haploid set of chromosomes.
Moreover, most of the bacterial genome consists of unique sequences, which include single-copy genes, ribosomal RNAs, and transfer RNAs. This contrasts with eukaryotic genomes that contain a significant amount of non-coding DNA, which does not encode for proteins.
Bacterial genomes are predominantly composed of unique sequences, and the variability in genome size often corresponds to the organism's dependence on a host for survival.