Anaerobic respiration is the production of Energy(ATP) in the absence of oxygen. Some dissimilatory metals reducing microorganisms reduces metals in the absence of oxygen during anaerobic respiration. These microorganisms use metals as terminal electron acceptor rather than molecular oxygen. These microbes use it to conserve energy by oxidizing organic materials and reducing metals.
Although the DNA packaging with histones proteins is mean to form nucleosomes (groups of 8 histones proteins), the higher structures why the genetic material is packaged with those molecules is to form chromosomes, as you said.
