C. Metabolic Diversity in Bacteria *Bacteria can be placed into 2 groups based on how they obtain energy : 1. Heterotrophs – get energy by consuming organic molecules made by other organisms. *Most prokaryotes are heterotrophs. 2. Autotrophs – get energy by making their own food from inorganic molecules.

Types of Heterotrophs : A. Chemoheterotrophs – organisms that must take in organic molecules for both energy & carbon. B. Photoheterotrophs – organisms that are photosynthetic but need organic compounds as a carbon source.

Types of Autotrophs A. Photoautotrophs – organisms that use energy from sunlight to convert CO2 & water to carbon compounds. B. Chemoautotrophs – organisms that make organic molecules from CO2 using energy from chemical reactions.

Releasing Energy -Bacteria, like all organisms, release energy through cellular respiration, fermentation, or both. Cellular respiration – process that releases energy by breaking down glucose & other food molecules in the presence of oxygen (O2). Fermentation – process by which cells release energy in the absence of O2.

Obligate aerobes vs. anaerobes -Organisms that require a constant supply of oxygen in order to live are called obligate aerobes, ex : Mycobacterium tuberculosis . -Organisms that must live in the absence of oxygen are called obligate anaerobes (oxygen would kill them), ex : Clostridium botulinum. -Organisms that can survive with or without oxygen are called facultative anaerobes, ex : E. coli. -Anaerobes perform fermentation to release energy & aerobes perform cellular respiration to release energy.

D. Bacterial Growth & Reproduction -Growth in bacteria is directly related to availability of food & production of waste products. Some divide every 20 minutes. Reproduction can occur by : 1. Binary fission – asexual reproduction in which an organism replicates it’s DNA & divides in half, producing 2 identical daughter cells. 2. Conjugation – sexual reproduction in which an organism exchanges genetic information.

Endospore Production -In poor environmental conditions, bacteria form spores that remain dormant for months, years, etc. until conditions become favorable again. Endospore – type of spore formed when a bacterium produces a thick internal wall that encloses its DNA & a portion of its cytoplasm.