The structures that help bacteria to attach to rocks and/or host tissue are

A. Holdfast

B. Rhizoids

C. Fimbriae

D. Mesosomes

Kingdom Monera is divided into three sub kingdoms that are cyanobacteria, archaebacteria and eubacteria (also known as true bacteria). Bacteria, especially pathogenic bacteria have filamentous appendages that help them to attach to the host cell. This filamentous structure is made up of pilin protein. This appendage is known as fimbriae. Fimbriae are shorter than pili. Pili is also made up of piling protein. Pili helps bacteria to transfer genetic material during conjugation. Rhizoid is a root-like structure present in liverwort, mosses, and fungi to provide attachment to the substance. Mesosomes help to increase the area of bacterial cells. It is a folded cavity or pouch in the cell membrane. Algae have a root-like structure for attachment with moist stones, soils, and wood. This root-like structure in algae is holdfast.

Archaebacteria: Their cell wall helps them to survive in extreme conditions. Archaebacteria cell walls are made up of branched-chain lipids. On the basis of their habitat, they are classified as methanogens, halophiles, and thermoacidophiles. Methanogens live in marshy habitat, Halophiles live in extreme saline habitats such as saline lake and sea, thermoacidophiles live in high temperatures as well as the high acidic environment.

Eubacteria: Eubacteria have cells made up of peptidoglycan (Amino acids and sugar). Eubacteria include cyanobacteria and mycoplasma. Mycoplasma does not have a cell wall, so they are also called bacteria with their coat off. They are also known as PPLO (Pleuropneumonia Like Organisms).