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Module: BIOM - 1009

Lecturer: Dr Peña-Fernández

Date: 07/10/16

Introduction to Microbes
o

Bacteria
 Bacteria are unicellular, prokaryotic organisms
that can be found in most places that meet their
individual requirements, usually warm, moist
environments
 Prokaryotic meaning no nucleus
 They are also both smaller than eukaryotes and only
range to a few micrometres in length
 They also have no membrane bound organelles
 They have 70s ribosomes as opposed to eukaryotic
80s ribosomes
 Bacteria come in a range of shapes:
 Rod shaped – Bacilli
 Round, circular shaped – Cocci
 Other shaped bacteria have been found too
 The right image is a scanning electron micrograph of Escherichia coli:

o

Archaea
 Archaea are another branch of unicellular prokaryotes
 Archaea were initially classified as being a subcategory of bacteria (named archaebacteria),
however there are many differences in the 2 domains that make it an outdated classification
 The differences range from morphological to physiological
 Some archaea are flat and square shaped, such as Haloquadratum walsbyi
 Another difference is that archaea rely on ether lipids in their cell membrane as
opposed to bacteria that rely ester lipids and peptidoglycan
 Finally, they are found in places that most bacteria cannot tolerate, such as hot
springs and volcanos
 The main difference that separates archaea as a new domain however, is their
differences in rRNA compared to bacteria or eukaryotes
o The 16s rRNA contains species specific information about protein production
o There tuned out to be a group of methanogens that differentiated
vastly to both eukaryotes and bacteria
 Methanogens are microorganisms that produce methane as a
metabolic by-product in anoxic conditions, they are exclusive to
archaea
 The following image shows a transmission electron micrograph of Methanosaeta harundinaceae

o

Fungi
 Fungi are a class of eukaryote, meaning they do have a nucleus and other membrane bound
organelles
 They can either be unicellular (such as mould)
or multicellular (such as mushrooms)
 There are many differences that isolate fungi as their
own kingdom compared to animals and plants
 Their cell wall is composed of chitin whereas
plants are made of cellulose

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