Download Bacteria - Part Two

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.