Chapter 2 - Review of general microbiology. Objectives Basic description of viruses, bacteria, fungi, algae, and protozoa (size, cell components) Basic functions of a bacterial cell Importance of the cell wall and cell membrane to a bacterial cell
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Oxygen atmosphere forms
4.5 4.0 3.0 2.0 1.0 0
Billions of years
A dividing gram positive bacterium
Size – ranges from 0.3 to 3mm in length depending on
106 bacteria in a pinpoint colony
106 bacteria/gm soil required to observe significant
Nitrosomonas vs. Pseudomonas
Specialist vs. Jack-of-all-Trades
Specializes in ammonia oxidation. These bacteria are important in
What are the basic functions of a microbial cell?
What are the basic components of a microbial cell?
Eubacteria have two main types of envelopes, Gram Positive and Gram Negative.
Cell membrane – The cell membrane is a highly selective barrier that enables cells to take in nutrients and excrete waste products
Cell surface meets the outside world
How does the cell membrane fit into the cell envelope?
Cells can have flagella that allow them to move over short distances (um) either toward nutrients or away from inhibitory substances.
Cells can have fimbriae that aid in attachment of cells to surfaces.
Nucleic acids –A,T (U), C, G
The chromosome of a bacterial cell contains approximately 3 x 106 base pairs. If stretched out, the chromosome is 1 mm in length. In actively growing cells there are 2 to 4 copies of the chromosome since several replicating forks can occur at the same time. Bacterial cells also contain small circular pieces of DNA called plasmids.
Cryptic plasmids no known function (most)
Resistance plasmids protect against antibiotics, metals, bacteriophage
Degradative plasmids encode biodegradation of unusual metabolites
Plant interactive plasmids mediate interaction between bacteria and plants
(Sym, Ti plasmids)
Miscellaneous plasmids involved in a variety of functions, RNA
metabolism, conjugation, bacterial cell
Types of plasmids
Low-copy –number plasmids 1-2 copies/cell, usually > 10 kb
High-copy-number plasmids 10 – 100 copies/cell, usually < 10kb
Relaxed plasmids not dependent on initiation of cell replication
Stringent plasmids synchronized with replication of chromosome
Conjugative plasmids self-transmissible between same/different
species, tra genes
Non-conjugative plasmids not self-transmissible
Incompatible plasmids cannot exist in together in the same cell
Inc P plasmids exist in a wide variety of bacteria
How was information transfer achieved?
DiGiovanni et al. 1996. Appl. Environ. Microbiol. 62:2521-2526.
Bacterial spore formers: Gram positive bacteria can form spores that are very resistant to heat, UV, and nutrient stress. Spores can even withstand autoclaving. As a result, soil must be autoclaved three times on consecutive days to achieve complete sterilization. This allows spores to germinate in between autoclaving events.
Heterotrophs (organic carbon)
Oxidation of inorganics
Viruses – living or nonliving?
Based on nutritional requirements which microbial groups might you find at the soil surface? At 100 ft below the surface?
Based on size which microbial groups might you find at the soil surface? At 100 ft below the surface?