Characteristics of the Microorganisms

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Characteristics of the Microorganisms
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Cells

• Marks the boundary between the living and the
  dead
• Structural and functional unit of an organism
• Smallest structure capable of performing all of
  the functions necessary for life

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All cells.

• Have an outer plasma membrane
• Contain DNA
• Enclosed within the cell somewhere
• Contain cytoplasm
• Everything between the plasma membrane and the
  region of DNA
• Gives cells their shape
• Assist in movement of cell and organelles

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Surface Area / Volume Ratio

• Actively metabolizing cells need to be small
• The amount of surface area affects the ability to
  get materials in and out of a cell
• cell in volume surface area

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Characteristics of Cells and Life

• All living things (single and multicellular) are
  made of cells that share some common
  characteristics
• basic shape
• spherical, cubical, cylindrical
• internal content
• cytoplasm, surrounded by a membrane
• DNA chromosome(s)
• ribosomes
• metabolic capabilities
• Two basic cell types eucaryotic and procaryotic

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Characteristics of Cells

• Eucaryotic cells
• Animals, plants, fungi, and protists
• contain double-membrane bound nucleus with DNA
• contain membrane-bound organelles

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Characteristics of Cells

• Procaryotic cells
• Bacteria and archaea
• no nucleus
• no membrane-bound organelles

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Characteristics of Life

• Growth and development
• Reproduction and heredity
• Metabolism
• Movement and/or irritability
• Cell support, protection, and storage mechanisms
• Transport of nutrients and waste

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External Structures

• Locomotor appendages
• flagella
• long, sheathed cylinder containing microtubules
• covered by an extension of the cell membrane
• function in motility
• cilia
• similar in overall structure to flagella
• shorter and more numerous
• found only on a single group of protozoa and
  certain animal cells
• function in motility, feeding and filtering

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External Structures

• Glycocalyx
• an outermost boundary that comes into direct
  contact with environment
• usually composed of polysaccharides
• appears as a network of fibers, a slime layer or
  a capsule
• functions in adherence, protection, and signal
  reception
• Beneath the glycocalyx
• Fungi and most algae have a thick, rigid cell
  wall
• Protozoa, a few algae, and all animal cells lack
  a cell wall and have only a membrane

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External Boundary Structures

• Cell wall
• Rigid, provides structural support and shape
• Fungi
• thick inner layer of polysaccharide fibers
• composed of chitin or cellulose and a thin layer
  of mixed glycans
• Algae
• varies in chemical composition
• substances include cellulose, pectin, mannans,
  silicon dioxide, and calcium carbonate

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External Boundary Structures

• Cytoplasmic (cell) membrane
• typical bilayer of phospholipids and proteins
• serves as selectively permeable barrier in
  transport
• Eucaryotic cells also contain membrane-bound
  organelles that account for 60-80 of their volume

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Prokaryote
Eukaryote
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Bacteria
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Bacterial Shapes, Arrangements, and Sizes

• Prokaryotes
• Typically described by one of three basic shapes
• coccus
• Spherical
• bacillus
• Rod
• coccobacillus
• vibrio
• spirillum
• helical, comma, twisted rod,
• Spirochete

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Bacterial Shapes, Arrangements, and Sizes

• Arrangement of cells dependent on pattern of
  division and how cells remain attached after
  division
• cocci
• singles
• diplococci
• tetrads
• irregular clusters
• chains
• cubical packets
• bacilli
• chains
• palisades

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The Cell Envelope

• External covering outside the cytoplasm
• Composed of two basic layers
• cell wall and cell membrane
• Maintains cell integrity
• Two generally different groups of bacteria
  demonstrated by Gram stain
• Gram-positive bacteria
• thick cell wall composed primarily of
  peptidoglycan and cell membrane
• Gram-negative bacteria
• outer cell membrane, thin peptidoglycan layer,
  and cell membrane

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Viruses
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General Structure of Viruses

• Size range
• most lt0.2 µm
• requires electron microscope
• Virion
• fully formed virus able to establish an infection

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General Structure of Viruses

• Capsids
• All viruses have capsids
• Constructed from identical subunits called
  capsomers
• made of protein
• nucleoscapsid
• Capsid nucleic acid
• Enveloped
• Naked

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General Structure of Viruses

• Two structural types
• Helical
• Continuous helix of capsomers forming a
  cylindrical nucleocapsid
• Icosahedral
• 20-sided with 12 corners
• vary in the number of capsomers
• Each capsomer may be made of 1 or several
  proteins
• Some are enveloped

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Helical- rod shaped capsomers that bind
together to form a series of hollow discs
resembling a bracelet
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Viral morphology (a) poxvirus, (b)
bacteriophage, (c) mumps, (d) herpesvirus, (e)
rhabdovirus, (f) HIV, (g) adenovirus, and (h)
papillomavirus.
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Eukaryotic cells and microorganisms
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Survey of Eucaryotic Microbes

• Fungi
• Algae
• Protozoa
• Parasitic worms

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Structures

• Appendages
• Glycocalyx
• Cell wall
• Cell membrane

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Fungi
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Kingdom Fungi

• 100,000 species divided into 2 groups
• macroscopic fungi (mushrooms, puffballs, gill
  fungi)
• microscopic fungi (molds, yeasts)
• Majority are unicellular or colonial
• Few have cellular specialization

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Microscopic Fungi

• Exist in two morphologies
• yeast
• hyphae
• Some exist in either form
• dimorphic
• characteristic of some pathogenic molds

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Fungal Nutrition

• All are heterotrophic
• Majority harmless saprobes
• Live off dead plants and animals
• Some are parasites
• Live on the tissues of other organisms, but none
  are obligate
• Mycoses
• Growth temperature 20o - 40oC
• Extremely widespread distribution in many habitats

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Fungal Reproduction

• Sexual reproduction
• Spores are formed following fusion of male and
  female strains and formation of sexual structure
• Sexual spores and spore-forming structures are
  one basis for classification
• Zygospores
• Ascospores
• Basidiospores
• Deuteromycota
• Asexual
• Majority are yeasts and molds
• Conidia

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Fungal Identification

• Isolation on specific media
• Macroscopic and microscopic observation of
• asexual spore-forming structures and spores
• hyphal type
• colony texture and pigmentation
• physiological characteristics
• genetic makeup

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Roles of Fungi

• Adverse impact
• mycoses, allergies, toxin production
• destruction of crops and food storages
• Beneficial impact
• decomposers of dead plants and animals
• sources of antibiotics, alcohol, organic acids,
  vitamins
• used in making foods and in genetic studies

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Protists
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Kingdom Protista

• Algae
• Protozoa

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Algae

• Photosynthetic organisms
• Kelps, seaweeds, euglenids, green algae, diatoms,
  dinoflagellates, brown algae, and red seaweeds
• Microscopic forms
• Unicellular
• Colonial
• filamentous
• Macroscopic forms
• colonial
• multicellular
• Contain chloroplasts with chlorophyll and other
  pigments
• Cell wall
• May or may not have flagella

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Algae

• Most are free-living in fresh and marine water
• Plankton
• Provide basis of food web in most aquatic
  habitats
• Produce large proportion of atmospheric O2
• Dinoflagellates
• Cause red tides and give off toxins
• Cause food poisoning with neurological symptoms
• Classified according to types of pigments and
  cell wall
• Used for cosmetics, food, and medical products

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Protozoa

• 65,000 species
• Vary in shape, lack a cell wall
• Most are unicellular
• Colonies are rare
• Most are harmless, free-living in a moist habitat
• Some are animal parasites
• Spread by insect vectors
• All are heterotrophic
• Feed by engulfing other microbes and organic
  matter

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Protozoa

• Most have locomotor structures
• flagella, cilia, or pseudopods.
• Exist as trophozoite
• motile feeding stage
• cyst
• Dormant resting stage when conditions are
  unfavorable for growth and feeding
• All reproduce asexually, mitosis or multiple
  fission
• Many also reproduce sexually
• conjugation

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Parasitic Helminths
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Parasitic Helminths

• Multicellular animals
• Parasitize host tissues
• Organs for reproduction, digestion, movement,
  protection
• Mouthparts
• Attachment
• Digestion of host tissues
• Well-developed sex organs that produce eggs and
  sperm
• Fertilized eggs go through larval period in or
  out of host body

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Helminths

• 50 species parasitize humans
• Acquired though
• Ingestion of larvae or eggs in food
• Soil or water
• Carried by insect vectors
• Afflict billions of humans
• Distributed worldwide
• Some restricted to certain geographic regions
• Higher incidence in tropics

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Life Cycles

• Hermaphroditic
• Transmission
• Definitive host
• Fertilized eggs

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Major Groups of Parasitic Helminths

• Flatworms
• no definite body cavity
• digestive tract a blind pouch
• simple excretory and nervous systems
• Groups
• cestodes (tapeworms)
• Trematodes or flukes, are flattened ,
  nonsegmented worms with sucking mouthparts.
• Roundworms (nematodes)
• round, a complete digestive tract
• protective surface cuticle
• spines and hooks on mouth
• excretory and nervous systems poorly developed

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Helminth Classification and Identification

• Classify according to
• shape, size, organ development, presence of
  hooks, suckers, or other special structures, mode
  of reproduction, hosts, and appearance of eggs
  and larvae
• Identify by
• microscopic detection of adult worm, larvae, or
  eggs

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Other infectious agents
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Unconventional Viruslike Agents

• cause spongioform encephalopathies
• transmissable, fatal, chronic infections of the
  nervous system
• Creutzfeldt-Jakob Disease (CJD)
• New variant CJD
• kuru
• caused by prions infectious proteins

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Prions

• Prions
• proteinaceous infectious particles
• misfolded proteins
• contain no nucleic acid
• cause transmissible spongiform encephalopathies
• common in animals
• Extremely resistant to usual sterilization
  techniques
• Cause transmissible spongiform encephalopathies
  (TSEs) in humans and animals
• Neurodegenerative diseases with long incubation
  periods

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Prions

• Variant CJD became apparent in the late 1990s
  after eating meat from cattle afflicted with
  bovine spongiform encephalopathy (BSE)
• Difficult to diagnose
• requires examination of biopsied brain or nervous
  tissue
• Prevention relies on avoidance of contaminated
  tissue
• Treatment focuses on easing symptoms

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New Variant Creutzfeldt-Jakob Disease (vCJD)

• Fatal brain disorder in humans