Copyright © 2010 Pearson Education, Inc. Microbial Growth  Increase in number of cells, not cell size  Populations  Colonies

Copyright © 2010 Pearson Education, Inc. The Requirements for Growth  Physical requirements  Temperature  pH  Osmotic pressure  Chemical requirements  Carbon  Nitrogen, sulfur, and phosphorous  Trace elements  Oxygen  Organic growth factor

Copyright © 2010 Pearson Education, Inc. Figure 6.1 Typical Growth Rates and Temperature

Copyright © 2010 Pearson Education, Inc. pH  Most bacteria grow between pH 6.5 and 7.5  Molds and yeasts grow between pH 5 and 6  Acidophiles grow in acidic environments

Copyright © 2010 Pearson Education, Inc. Osmotic Pressure  Hypertonic environments, or an increase in salt or sugar, cause plasmolysis  Extreme or obligate halophiles require high osmotic pressure  Facultative halophiles tolerate high osmotic pressure

Copyright © 2010 Pearson Education, Inc. Culture Media  Culture medium: Nutrients prepared for microbial growth  Sterile: No living microbes  Inoculum: Introduction of microbes into medium  Culture: Microbes growing in/on culture medium

Copyright © 2010 Pearson Education, Inc. Agar  Complex polysaccharide  Used as solidifying agent for culture media in Petri plates, slants, and deeps  Generally not metabolized by microbes  Liquefies at 100°C  Solidifies at ~40°C

Copyright © 2010 Pearson Education, Inc. Chemical Requirements  Carbon  Structural organic molecules, energy source  Chemoheterotrophs use organic carbon sources  Autotrophs use CO 2

Copyright © 2010 Pearson Education, Inc. Chemical Requirements  Nitrogen  In amino acids and proteins  Most bacteria decompose proteins  Some bacteria use NH 4 + or NO 3 –  A few bacteria use N 2 in nitrogen fixation

Copyright © 2010 Pearson Education, Inc. Chemical Requirements  Sulfur  In amino acids, thiamine, and biotin  Most bacteria decompose proteins  Some bacteria use SO 4 2– or H 2 S  Phosphorus  In DNA, RNA, ATP, and membranes  PO 4 3– is a source of phosphorus

Copyright © 2010 Pearson Education, Inc. Chemical Requirements  Trace elements  Inorganic elements required in small amounts  Usually as enzyme cofactors

Copyright © 2010 Pearson Education, Inc.

Figure 6.10 Selective Media  Suppress unwanted microbes and encourage desired microbes

Copyright © 2010 Pearson Education, Inc. Figure 6.12a Binary Fission

Copyright © 2010 Pearson Education, Inc. Figure 6.12b Binary Fission

Copyright © 2010 Pearson Education, Inc. Figure 6.13b Cell Division

Copyright © 2010 Pearson Education, Inc. Figure 6.14 Bacterial Growth Curve

Copyright © 2010 Pearson Education, Inc. Figure 6.15 ANIMATION Bacterial Growth Curve Phases of Growth

Copyright © 2010 Pearson Education, Inc. Figure 6.16 Plate Counts  After incubation, count colonies on plates that have 25–250 colonies (CFUs)

Copyright © 2010 Pearson Education, Inc. Figure 6.18 Counting Bacteria by Membrane Filtration

Copyright © 2010 Pearson Education, Inc. Figure 6.20 Direct Microscopic Count

Copyright © 2010 Pearson Education, Inc. Direct Microscopic Count

Copyright © 2010 Pearson Education, Inc. Figure 6.21 Turbidity

Copyright © 2010 Pearson Education, Inc. Figure 6.21 Turbidity

Copyright © 2010 Pearson Education, Inc. Measuring Microbial Growth Direct Methods  Plate counts  Filtration  MPN  Direct microscopic count Indirect Methods  Turbidity  Metabolic activity  Dry weight

Copyright © 2010 Pearson Education, Inc. History of Viruses  Viruses have long been around – we just started studying them in the twentieth century.  1930s – term “virus” used (Latin: poison)  1935 – Wendell Stanley (American chemist) isolated the tobacco mosaic virus  1930s electron microscope invented!

Copyright © 2010 Pearson Education, Inc. General Characteristics of Viruses  How would you define a virus?  Contain a single type of nucleic acid (DNA or RNA, not both!)  Protein coat  Intracellular parasites  No ribosomes  Host range – most viruses infect only specific types of cells  Size: nm in length (smallest infectious agent)  Not a cell  How would you define a virus?  Contain a single type of nucleic acid (DNA or RNA, not both!)  Protein coat  Intracellular parasites  No ribosomes  Host range – most viruses infect only specific types of cells  Size: nm in length (smallest infectious agent)  Not a cell

Copyright © 2010 Pearson Education, Inc. relative sizes

Copyright © 2010 Pearson Education, Inc. Viruses vs. Bacteria

Copyright © 2010 Pearson Education, Inc. Viral Structure  1. Nucleic Acids  Double-stranded DNA  Double stranded RNA  Single strand of DNA  Single strand of RNA Can be linear or circular strand Can be broken up in several pieces Can be linear or circular strand Can be broken up in several pieces 2.Capsid – Protein coat surrounding the nucleic acid of a virus some capsids are enclosed by an envelope (lipids, proteins & carbs) 2.Capsid – Protein coat surrounding the nucleic acid of a virus some capsids are enclosed by an envelope (lipids, proteins & carbs) The capsid is composed of subunits called CAPSOMERS (those can be just one type of protein or several types of proteins) Spike s!

Copyright © 2010 Pearson Education, Inc.

Viral Structure & Infections  Host gets infected by virus -> host produces antibodies (proteins that react with the surface proteins of the virus) -> virus becomes inactivated/ infection stopped!  So why can you get the flu more than once if you’ve already developed antibodies for the virus?  B/c of mutations in the genes that code for for the viruses’ surface proteins -> altered surface proteins ->antibodies no longer react against them.  Influenza frequently undergoes changes in its spikes!

Copyright © 2010 Pearson Education, Inc. Morphology of Viruses  Enveloped Viruses (spherical)  Most common type  Influenza  Helical Viruses  Polyhedral Viruses  Complex Viruses

Copyright © 2010 Pearson Education, Inc. Helical virus  Long rods – rigid or flexible  Examples:  ebola hemorrhagic fever  rabies

Copyright © 2010 Pearson Education, Inc. Polyhedral Viruses Examples: adenovirus poliovirus

Copyright © 2010 Pearson Education, Inc. Complex Viruses Examples: Bacterio phages

Copyright © 2010 Pearson Education, Inc. Viral escape – presence or absence of envelope  Two methods by which mature viruses escape their host cell 1. Host cell lysis - releases naked or non-enveloped viruses 2. Budding – virus passes through cell membrane – takes part of host cell’s membrane – envelope is formed around capsid

Copyright © 2010 Pearson Education, Inc. The Lytic Cycle  Attachment: Phage attaches by tail fibers to host cell  Penetration: Phage lysozyme opens cell wall; tail sheath contracts to force tail core and DNA into cell  Biosynthesis: Production of phage DNA and proteins  Maturation: Assembly of phage particles  Release: Phage lysozyme breaks cell wall

Copyright © 2010 Pearson Education, Inc. Figure A Viral One-Step Growth Curve

Copyright © 2010 Pearson Education, Inc. Lytic Cycle of a T-Even Bacteriophage Figure 13.11

Copyright © 2010 Pearson Education, Inc. 4 Figure Lytic Cycle of a T-Even Bacteriophage

Copyright © 2010 Pearson Education, Inc. Results of Multiplication of Bacteriophages  Lytic cycle  Phage causes lysis and death of host cell  Lysogenic cycle  Prophage DNA incorporated in host DNA  Phage conversion  Specialized transduction ANIMATION Viral Replication: Temperate Bacteriophages ANIMATION Viral Replication: Virulent Bacteriophages

Copyright © 2010 Pearson Education, Inc. Figure The Lysogenic Cycle

Copyright © 2010 Pearson Education, Inc Figure 8.28 Generalized Transduction

Copyright © 2010 Pearson Education, Inc. Figure Specialized Transduction

Copyright © 2010 Pearson Education, Inc Specialized Transduction ANIMATION Transduction: Specialized Transduction ANIMATION Transduction: Generalized Transduction

Copyright © 2010 Pearson Education, Inc. Multiplication of Animal Viruses  Attachment: Viruses attach to cell membrane  Penetration by endocytosis or fusion  Uncoating by viral or host enzymes  Biosynthesis: Production of nucleic acid and proteins  Maturation: Nucleic acid and capsid proteins assemble  Release by budding (enveloped viruses) or rupture

Copyright © 2010 Pearson Education, Inc. Figure 13.14a Attachment, Penetration, Uncoating  By pinocytosis

Copyright © 2010 Pearson Education, Inc. Figure 13.14b Attachment, Penetration, Uncoating  By fusion

Copyright © 2010 Pearson Education, Inc. Figure Budding of an Enveloped Virus

Copyright © 2010 Pearson Education, Inc. Figure Budding of an Enveloped Virus

Copyright © 2010 Pearson Education, Inc. ANIMATION Viral Replication: Animal Viruses ANIMATION Viral Replication: Overview