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Short review of chapters 8-15

Symbiotic Relationships

"Symbiosis means “to live together”

Describes the relationship between microorganisms and their host

3 types

Mutualism

“Normal flora”

Commenalism

Transient flora

Parasitism

pathogens

Portals of Entry

Sites through which pathogens enter the body

4 major types

Skin

Mucous membranes

Placenta

Parenteral route

Manifestations of Disease:

Symptoms-

subjective characteristics of disease felt only by the patient

Signs-

objective manifestations of disease that can be observed or measured by others

Syndrome-

group of symptoms and signs that characterize a disease or abnormal condition

Asymptomatic, or subclinical-

infections lack symptoms but may still have signs of infection

Virulence Factors of Infectious Disease

"Virulence factors contribute to an organisms pathogenicity(ability to cause disease)

Adhesion factors

Extracellular enzymes

Toxins

Antiphagocytic factors

Extracellular Enzymes

Reservoirs of Infection

Animal reservoir

Human carriers

Nonliving reservoir

Nonspecific Lines of Defense

First Line of Defense

Structures, chemicals, processes that work to prevent pathogens entering the body

Skin

Dermis & epidermis

Chemicals

sweat, sebum

Mucous membranes

Competition by normal flora

Second line of defense

cells

RBC’s, platelets, leukocytes

antimicrobial chemicals

secreted by some organs

processes

phagocytosis

natural killer cells

inflammation

fever

Drugs

•• Chemicals that affect physiology in any manner

•• Chemotherapeutic agents – drugs that act against diseases

•• Antimicrobial agents – drugs that treat infections

Mechanisms of Antimicrobial Action

•• Key is selective toxicity

Inhibition of Cell Wall Synthesis

Inhibition of Protein Synthesis

Disruption of Cytoplasmic Membranes

Inhibition of Metabolic Pathways

Inhibition of Nucleic Acid Synthesis

Prevention of Virus Attachment

The Development of Resistant Organisms in Populations

Prokaryotes

Most diverse group of organisms on Earth

Only a few capable of colonizing humans and causing disease

Reproduction of Prokaryotic Cells

All reproduce asexually

Arrangements of Prokaryotic Cells

Result from two aspects of division during binary fission

" " Planes in which cells divide

" " Separation of daughter cells

Modern Prokaryotic Classification

Currently based on genetic relatedness of rRNA sequences

Three domains

" " Archaea

" " Bacteria

" " Eukarya

Survey of Archaea

Lack peptidoglycan
No known human pathogens

Extremophiles

Non-Archaea Prokaryotes:

Deeply Branching Bacteria

" " Scientists believe these organisms are similar to earliest bacteria

Phototrophic Bacteria

Low G + C Gram-Positive Bacteria

" " Clostridia

" " Mycoplasma

" " Low C + C Gram-positive bacilli and cocci

" " Bacillus

" " Listeria

" " Lactobacillus

" " Streptococcus and Enterococcus

" " Staphylococcus

Endospores

" " Produced by Gram-positive Bacillus and Clostridium

" " Constitute a defensive strategy against hostile or unfavorable conditions

" " Extremely resistant to drying, heat, radiation, and lethal chemicals

" " Can remain viable for tens to thousands of years

" " Serious concern to food processors, health care professionals, and governments

High G + C Gram-Positive Bacteria

" " Includes rod-shaped cells and filamentous bacteria

" " Corynebacterium

" " Mycobacterium

" " Actinomycetes

" " Actinomyces

" " Nocardia

" " Streptomyces

Gram-Negative Proteobacteria

" " Largest and most diverse group of bacteria

"" Alphaproteobacteria

"" Betaproteobacteria

"" Gammaproteobacteria

"" Deltaproteobacteria

"" Epsilonproteobacteria

Other Gram-Negative Bacteria

" " Chlamydias

" " Chlamydia

" " Spirochetes

" " Treponema

" " Borrelia

" " Bacteroids

" " Bacteroides

" " Cytophaga

Characterizing and Classifying Eukaryotes

Eukaryotes

" " Four major groups

" " Protozoa

" " Fungi

" " Algae

" " Walter Molds and Slime Molds

" " Include both human pathogens and organisms vital for human life

Reproduction in Eukaryotes

" " More complicated than that in prokaryotes

Nuclear Division

" " Two types

" " Mitosis

" " Meiosis

Schizogony

Classification of Eukaryotic Organisms

Protozoa

" " Diverse group defined by three characteristics

" " Eukaryotic

" " Unicellular

" " Lack a cell wall

Distribution of Protozoa

Require moist environments; Most live worldwide in ponds, streams, lakes, and oceans; critical members of plankton

Morphology of Protozoa

Characterized by great morphologic diversity

All produce trophozoites; some produce cysts

Nutrition of Protozoa

" " Most are chemoheterotrophic

Reproduction in Protozoa

" " Most reproduce asexually only (binary fission or schizogony)

" " Few also have sexual reproduction

" " Some become gametocytes that fuse to form diploid zygote

" " Some utilize a process called conjugation

Fungi

Chemoheterotrophic

Lack chlorophyll; do not perform photosynthesis

Significance of Fungi

Decompose dead organisms and recycle their nutrients

Form beneficial associations with roots of vascular plants that help plant absorb water and minerals

Used for food, in religions ceremonies, and in manufacture of foods and beverages

Produce antibiotics

Nutrition of Fungi

Acquire nutrients by absorption

Most are aerobic; some are anaerobic; many yeasts are facultative anaerobes

Reproduction of Fungi

All have some means of asexual reproduction involving mitosis and cytokinesis

Most also reproduce sexually

Budding and Asexual Spore Formation

Yeasts bud in manner similar to prokaryotic budding

Filamentous fungi produce lightweight spores that differ in mode of development

Lichens

Partnerships between fungi and photosynthetic microbes (green algae or cyanobacteria)

Grow on soil, rocks, leaves, tree bark, other lichens; almost every habitat

Algae

Simple, eukaryotic, phototrophic organisms that carry out oxygenic photosynthesis using chlorophyll a

Distribution and Morphology of Algae

" " Most are aquatic, living in the photic zone of fresh, brackish, and salt water

Reproduction in Algae

" " Asexual reproduction in unicellular algae involves mitosis followed by cytokinesis

Water Molds

" " Differ from fungi

Water Molds

" " decompose dead material

" " recycle nutrients into the environment

" " pathogens of crops

" " cause of Irish potato famine

Slime Molds

" " Differ from fungi in two main ways

" " Lack cell walls

" " Nutrition is phagocytic rather than absorptive

Parasitic Helminths and Vectors

" " Parasitic worms have microscopic infective and diagnostic stages – usually eggs or larvae

" " Vectors are animals such as ticks, lice, and mosquitoes that carry and transmit microscopic pathogens

Viruses

" Cause many infections of humans, animals, plants, and bacteria

" Cannot carry out any metabolic pathway

" Neither grow nor respond to the environment

" Cannot reproduce independently

" Obligate intracellular parasites

Characteristics of Viruses

" Virus – miniscule, acellular, infectious agent having one or several pieces of either DNA or RNA

" Have extracellular and intracellular state

Characteristics of Viruses

" Extracellular state

" Called virion

" Protein coat (capsid) surrounding nucleic acid

" Nucleic acid and capsid also called nucleocapsid

" Some have phospholipid envelope

" Outermost layer provides protection and recognition sites for host cells

" Intracellular state

" Capsid removed

" Virus exists as nucleic acid

How Viruses Are Distinguished

" Type of genetic material they contain

" Kinds of cells they attack

" Size of virus

" Nature of capsid coat

" Shape of virus

" Presence or absence of envelope

Genetic Material of Viruses

" May be DNA or RNA; never both

" Primary way scientists categorize and classify viruses

" Can be dsDNA, ssDNA, dsRNA, ssRNA

Hosts of Viruses

" Most only infect particular kinds of host’s cells

" May only infect particular kind of cell in host

Capsid Morphology

" Capsids – protein coats that provide protection for viral nucleic acid and means of attachment to host’s cells

The Viral Envelope

" Acquired from host cell during viral replication or release; envelope is portion of membrane system of host

" Envelope’s proteins and glycoproteins often play role in host recognition

Viral Replication-lytic and lysogeny

" Dependent on host’s organelles and enzymes to produce new virions

" Replication cycle usually results in death and lysis of host cell

" Stages of lytic replication cycle

" Attachment

" Entry

" Synthesis

" Assembly

" Release

Attachment of Animal Viruses

" Chemical attraction

" Animal viruses do not have tails or tail fibers

" Have glycoprotein spikes or other attachment molecules that mediate attachment

Assembly and Release of Animal Viruses

" Naked viruses released by exocytosis or may cause lysis and death of host cell

Latency of Animal Viruses

animal viruses can remain dormant in host cells

" May be prolonged for years with no viral activity, signs, or symptoms

The Role of Viruses in Cancer

" Several DNA and RNA viruses are known to cause ~15% of human cancers

" Burkitt’s lymphoma

" Hodgkin’s disease

" Kaposi’s sarcoma

" Cervical cancer

Culturing Viruses in the Laboratory

In Whole Organisms

Bacteria

Plants and Animals

Characteristics of Viroids

" Extremely small, circular pieces of RNA that are infectious and pathogenic in plants

" Similar to RNA viruses, but lack capsid

Characteristics of Prions

" Proteinaceous infectious agents

" Composed of single protein PrP

Characteristics of Prions

" When prions present, they cause newly synthesized cellular PrP to refold into prion PrP

Prion Diseases

All involve fatal neurological degeneration, deposition of fibrils in brain, and loss of brain matter

Large vacuoles form in brain; characteristic spongy appearance

Spongiform encephalopathies – BSE, CJD, kuru

Only destroyed by incineration; not cooking or sterilization

Controlling Microbial Growth in the Environment

•Sterilization

•Disinfection(disinfectants)

•Antisepsis(antiseptic)

•Degerming

•Sanitization

•Pasteurization

Physical Methods of Microbial Control
Chemical Methods of Microbial Control

Action of Antimicrobial Agents

•Modes of action fall into two basic categories

•Alteration of cell walls or cytoplasmic membranes

•Interference with protein and nucleic acid structure

Recombinant DNA Technology

Three Goals of Recombinant DNA Technology

Eliminate undesirable phenotypic traits in humans, animals, plants, and microbes

Combine beneficial traits of two or more organisms to create valuable new organisms