Kingdom Monera

  General

· Prokaryote means “before a nucleus.”

·  Prokaryotes are single-celled organisms. They are the smallest, simplest organisms.

· The group includes

i.         Archaebacteria - Found in anaerobic conditions with high [salt], high temperature, and low pH. These are believed to be the conditions on the early Earth. Earth?s early atmosphere did not contain oxygen. The earliest organisms were anaerobic.

                        ii.        Eubacteria - This group includes the traditional bacteria and is the largest of the two.

· They are found in nearly every habitat studied, including some that no other organism is able to withstand.

·  Bacteria have a cell wall, a cell membrane surrounds the cell but no membrane-bound organelles such as a nucleus, mitochondria, chloroplasts, Golgi apparatus, or ER. Some are covered by a layer of “slime” called a capsule. Some have flagella for locomotion.

·  They show 3 basic shapes

i.         Cocci - spherical

                        ii.        Bacilli - rod-shaped

                        iii.       Spirilla - spiral

 Respiration

· Obligate aerobes - must have oxygen.

· Obligate anaerobes - cannot survive in the presence of oxygen.

·  Facultative anaerobes - will use oxygen if present but don’t need it.

 Nutrition

· Most are heterotrophs although some are autotrophs. The autotrophic bacteria either use chemicals as a source of energy (chemoautotrophs) or are photosynthetic (photoautotrophs).

·  Some are parasites which live off a living host.

· Some are saprobes, feeding off dead organisms and waste (i.e., decomposers).

 Reproduction

· Prokaryotes have a single circular chromosome attached to the inside of the plasma membrane.

·  Asexual - binary Fission

i.         Prokaryotes reproduce by simply splitting in two.

                        ii.        The DNA is copied and the cell divides into two identical cells.

· Sexual - conjugation

i.         Sexual reproduction combines genes from two different individuals and increases variation. Prokaryotes do not technically reproduce sexually can mix genes with one another.

                        ii.        Conjugation - Two cells join briefly and one cell donates some DNA (called a plasmid) to the other one. Sometimes part of the cell’s chromosome is donated as well.

                        iii.       Transformation - Bacteria can also pick up pieces of DNA from the environment.

                        iv.       Transduction - sometimes viruses transfer pieces of DNA from one cell to another.

· Mutation is a large source of genetic diversity in bacteria.

· Endospores

i.         some bacteria form endospores when environmental conditions become unfavorable.

                        ii.        Endospores are DNA and a small amount of cytoplasm enclosed in a tough cell wall. They are resistant to extremes in temperature, drying, and harsh chemicals.