BACTERIA An Overview Staphlococcus aureus and human white blood cells.
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Transcript of BACTERIA An Overview Staphlococcus aureus and human white blood cells.
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BACTERIABACTERIAAn OverviewAn Overview
Staphlococcus aureus and human white
blood cells
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Bacteria are
single-celled,
microscopic,
prokaryotic organisms
that we rely on and fight on a daily basis
“On any possible, reasonable or fair criterion, bacteria are—and always have been—the dominant forms of life on Earth.” – Stephen Jay Gould, 1996
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Basic Characteristics:
Prokaryotic- no true nucleus, no membrane-bound organelles – different from eukaryotes (which make up all multi-cellular organisms and lots of single-celled organisms, too)
Single-celled organisms
Cell walls contain a peptidoglycan – aka murien – a polymer of sugars and acids found only in bacteria that forms a meshlike layer protecting the cell membrane
Tiny - measured in units called micrometers (μm - 1 micrometer = 0.0001 cm)
Lack a true nucleus; instead, have a region called the ‘nucleoid region‘where DNA congregates
DNA is free floating (no membrane surrounding DNA)
May have additional DNA which is not associated with this nucleoid region (called a plasmid)
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Other Characteristics:
Rapid growth and cell division (binary fission) under favorable conditions
Mutants that arise from bacteria can become extremely resilient organisms because bacteria can:
Grow and reproduce cells quickly
Adapt quickly to changing environments
Plasmids impart additional resistant characteristics to bacteria via cell-to-cell transfer of this extra DNA material
Capable of colonizing in almost any environment
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The overall form of a basic bacterial cell is that of a complex cell envelope that encloses cell cytoplasm. Cell appendages from the envelope protrude into the environment surrounding the cell.
Parts of a bacterial cell:
Pili: hair-like appendages used for pulling bacteria along surfaces or to exchange genetic information (plasmids) – sex pili
Fimbriae: filamentous protein outgrowths from cell envelope used to adhere to one another and to other cells
Capsule: Attachment to surfaces; protection against phagocytic engulfment, occasionally killing or digestion; reserve of nutrients or protection against desiccation
Cell wall: found on all bacteria – can be thick or thin – thick = Gram +ve, thin = Gram –ve due to response to Gram stain
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Outer membrane and Plasma membrane : Permeability barrier; transport of nutrients and wastes; energy generation; location of numerous enzyme systems - outer membrane in Gram –ve species only
Cytoplasm: aqueous solution that bathes and surrounds everything inside the cell
Nucleoid region: DNA gathers here
Plasmids: DNA that can be copied and passed to other bacteria without going through reproduction
Ribosomes: Protein synthesis
Flagellum: long, whip-like appendage used for locomotion
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Bacteria are one of the three domains – we further classify bacteria into phyla, class, order, family, genus, species as best we can, based on many different characteristics. We will cover the basic characteristics useful in classifying pathogenic bacteria.
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Classifying Bacteria
Most microbiologists classify bacteria according to a phylogenetic classification system based on Bergey's Manual of Systematic Bacteriology (Bergey's Manual). The Bergey's Manual is a guide to distinguishing bacterial species based on phenotypic differences. For our purpose, and for simplicity's sake, we will use a more basic classification approach.
We can classify bacteria according to:
ShapeCell wall structure and the Gram StainCellular respiration
Public Health and Doctors also use Growth Media as an indicator
A couple of other criteria for classification:Forming endosporesMycolic acids
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SHAPE
Cocci: spherical shape
Bacillus: rod shape
Spirochetes: spiral shape
3 general shapes:
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GRAM STAINS
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CAPSULES
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USE OF OXYGEN (RESPIRATION)
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PUTTING IT ALL TOGETHER - CLASSIFYING
Domain: BacteriaKingdom: BacteriaPhylum: ProteobacteriaClass: Gamma ProteobacteriaOrder: EnterobacterialesFamily: EnterobacteriaceaeGenus: EscherichiaSpecies: Escherichia coli (E. coli)
E. coli in intestine of a human
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SEROTYPES
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Try to match the following by using your new classification skills: