Prokaryotes, Eukaryotes, and Non-living Infectious Particles

Introduction to MicrobiologyCommon Pathogens

The Prokaryotes

Proteobacteria

• All Gram-negative• Many pathogens. Also organisms that do

nitrogen fixation• Most use flagella for movement; some non-

motile or use gliding motility• Alpha, Beta, Gamma, Delta and Epsilon

Alphaproteobacteria Rickettsiaceae; Cell Symbionts

Bartonella – causes cat scratch disease

Betaproteobacteria

• Aerobic or facultative bacteria that are often highly versatile in their degradation capacities

• Contains mostly human pathogens– Example: Neisseria species.

Figure 24.7

The Betaproteobacteria• Bordetella

– Chemoheterotrophic; rods

– B. pertussis

• Burkholderia– Nosocomial

infections

Gammaproteobateria

• Class of several medically, ecologically and scientifically important groups of bacteria

• Includes Pseudomonas aeruginosa, Vibrio species (Cholera), E. coli, Salmonella species, Shigella species, etc.

Figure 11.7

The Gammaproteobacteria

• Pseudomonadales– Pseudomonas

• Opportunistic pathogens

• Metabolically diverse

• Polar flagella

Figure 11.8

The Gammaproteobacteria• Vibrionales

– Found in coastal water

• Vibrio cholerae causes cholera

• V. parahaemolyticus causes gastroenteritis

The Gammaproteobacteria• Enterobacteriales

(enterics)– Peritrichous flagella;

facultatively anaerobic

• Enterobacter• Erwinia• Escherichia• Klebsiella• Proteus• Salmonella• Serratia• Shigella• Yersinia

Figure 11.9b

More Gammaproteobacteria

Yersinia Pestis – causative agent of the Black Plague

Yersinia enterocoliticaCauses Yersinosis; enterocolitis. Zoonotic disease.

Figure 11.12

The Epsilonproteobacteria

• Helicobacter– Multiple flagella – Peptic ulcers– Stomach cancer

Epsilonproteobacteria

• Mainly the curved/spirilla• Most of the known species inhabit the

digestive tract of animals and serve as symbionts or pathogens(– Helicobacter spp. in the stomach– Campylobacter spp. in the duodenum.

Epsilonproteobacteria

• Campylobacter jejuni – causes food borne intestinal illness.

Gram-Positive Bacteria - Firmicutes

• Low G + C• Gram-positive

Figure 11.15

ClostridialesGram positive; spore producers; obilgate

anaerobes• Clostridium

Gangrene – caused by C. perfringens

Figure 11.18

Bacillales Gram positive; aerobic of facultative anaerobes; Bacillus, Listeria

and Staphylococcus

• Staphylococcus– Cocci

Staph Infection

[Insert Figure 11.19]

Figure 11.19

Lactobacillales• Generally

aerotolerant anaerobes; lack an electron-transport chain– Lactobacillus– Streptococcus– Enterococcus– Listeria

Actinobacteria

• High G + C• Gram-positive

Actinobacteria

• Actinomyces• Corynebacterium• Frankia• Gardnerella• Mycobacterium• Nocardia• Propionibacterium• Streptomyces

Figure 11.24b

Chlamydiasobligate intacelluar parasites; unique life cycles

• Chlamydia trachomatis– Trachoma– STI, urethritis

• Chlamydophila pneumoniae

• Chlamydophila psittaci – Psittacosis

Figure 11.24a

Life Cycle of the Chlamydias

Figure 11.25

SpirochetesAll posses axial filaments

• Borrelia• Leptospira• Treponema

Bacteroidetes

• Gram negative, non-sporeforming, anaerobic, and rod-shaped bacteria that are widely distributed in the environment, including in soil, in sediments, sea water and in the guts and on the skin of animals.

• Bacteroides are found in the mouth and large intestine

• Cytophaga: Cellulose-degrading in soil

Figure 11.26

Fusobacteria- Fusobacterium is a Gram-

negative non-sporeforming bacterium that is widely known and studied as a human and animal pathogen.

- Fusobacterium's exceptional ability to adhere with both Gram-negative and Gram-positive plaque microorganisms in biofilms (specifically in soft tissue) has made it a highly invasive pathogen.

- Primarily given attention for its peridontal implications

- Strains of Fusobacterium have been identified as pathogen to many parts of the body

Domain Archaea

Extremophiles• Hyperthermophiles

– Pyrodictium– Sulfolobus

• Methanogens– Methanobacterium

• Extreme halophiles– Halobacterium

Microbial Diversity

• PCR indicates up to 10,000 bacteria per gram of soil.

• Many bacteria have not been identified because they– Haven't been cultured– Need special nutrients– Are a part of complex food chains requiring the

products of other bacteria– Need to be cultured to understand their metabolism

and ecological role

The Eukaryotes: Fungi, Algae, Protozoa, and Helminths

Kingdom Fungi

Nutritional Type Chemoheterotroph

Multicellularity All, except yeasts

Cellular ArrangementUnicellular, filamentous, fleshy

Food Acquisition Method Absorptive

Characteristic Features Sexual and asexual spores

Embryo Formation None

Mycology is the study of fungi

Fungi

Figure 12.2

Molds

• The fungal thallus consists of hyphae; a mass of hyphae is a mycelium.

Figure 12.3

Yeasts

• Unicellular fungi• Fission yeasts divide symmetrically• Budding yeasts divide asymmetrically

Figure 12.4

Fungal Dimorphism

• Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C

Medically Important Phyla of Fungi

• Zygomycota – saprophtyic molds (bread mold); mucor• Ascomycota – sac fungi; Candida albicans and

Aspergillus flavus• Anamorphs – produce asexual spores only; ringworm

(tinea) and dermatophytes– Basidiomycota – club fungi– Teleomorphic fungi – produce sexual and asexual

spores• Cryptococcus (yeast-like state causes disease)

Zycomycota - Mucormycosis

Dermatophyte – capable of utilizing keratin

Cryptococcus

Aspergillosis

Candidiasis

Kingdom Protist

Nutritional Type Photoautotroph

Multicellularity Some

Cellular ArrangementUnicellular, colonial, filamentous, tissues

Food Acquisition Method Diffusion

Characteristic Features Pigments

Embryo Formation None

Algae

Diatoms – produce neurotoxins

Figure 12.13

Dinoflagellates• Cellulose in plasma

membrane• Unicellular• Chlorophyll a and c,

carotene, xanthins• Store starch• Some are symbionts in

marine animals• Neurotoxins cause

paralytic shellfish poisoning

Figure 12.14

Oomycota• Decomposers and

plant parasites– Phytophthora

infestans responsible for Irish potato blight

– P. cinnamoni infects Eucalyptus

– P. ramorum causes sudden oak death

Kingdom Protist

Nutritional Type Chemoheterotroph

Multicellularity None

Cellular Arrangement Unicellular

Food Acquisition Method Absorptive; ingestive

Characteristic Features Motility; some form cysts

Embryo Formation None

Protozoa

Medically Important Phyla of Protozoa

• Archaezoa• Microspora• Amoebozoa• Apicomplexa• Ciliophora• Euglenozoa

Figure 12.16b

Archaezoa• No mitochondria• Multiple flagella• Giardia lamblia• Trichomonas

vaginalis (no cyst stage)

Figure 12.16c, d

Archaezoa

Microspora Opportunistic parasites. Intracelluar development and

spore formation• Microsporidia

Figure 12.17a

Amoebozoa• Move by

pseudopods• Entamoeba• Acanthamoeba

Apicomplexa

• Nonmotile• Intracellular parasites• Complex life cycles• Plasmodium• Babesia• Cryptosporidium• Cyclospora

2

3

67

8

Figure 12.18

The Life Cycle of Plasmodium vivax

Clinical Focus, p. 355

Cryptosporidium

Figure 12.19

Ciliates• Move by cilia• Complex cells• Balantidium

coli is the only human parasite

Figure 12.20

Euglenozoa

• Move by flagella• Euglenoids

– Photoautotrophs

Figure 23.22

Euglenozoa• Move by flagella• Hemoflagellates

– Trypanosoma spp.• Sleeping

sickness• Chagas’ disease

Kingdom Animalia

Nutritional Type Chemoheterotroph

Multicellularity All

Cellular Arrangement Tissues and organs

Food Acquisition Method Ingestive; absorptive

Characteristic Features Elaborate life cycles

Embryo Formation All

Helminths

Helminths (Parasitic Worms)

• Kingdom: Animalia– Phylum: Platyhelminthes (flatworms)

• Class: Trematodes (flukes)– Tissue and blood flukes

• Class: Cestodes (tapeworms)

– Phylum: Nematoda (roundworms)

Characteristics of Helminths

• Reduced digestive system• Reduced nervous system• Reduced locomotion• Complex reproduction

Figure 12.25

The Life Cycle of Trematodes

Figure 12.26

Cestodes, or Tapeworms

Human as

Definitive Host – parasite reaches maturity

Taenia saginata Cysticerci in beef muscle

Intermediate Host – only some of the parasite’s developmental stages are complete

Echinococcus granulosus

Adult in dog

Figure 12.28

Nematodes

Figure 12.29

The Heartworm Dirofilaria immitis

Ascaris and Pinworm

Arthropods as Vectors

• May transmit diseases (vectors) • Kingdom: Animalia

– Phylum: Arthropoda (exoskeleton, jointed legs)• Class: Insecta (6 legs)

– Lice, fleas, mosquitoes

• Class: Arachnida (8 legs)– Mites and ticks

Figure 12.31

Arthropods as Vectors

Viruses

• Obligatory intracellular parasites• Contain DNA or RNA• Contain a protein coat• Some are enclosed by an envelope• Some viruses have spikes• Most viruses infect only specific types of cells

in one host• Host range is determined by specific host

attachment sites and cellular factors

Structure

Figure 13.2a

• Nucleic acid– DNA or RNA

• Capsid– Capsomeres

• Envelope• Spikes

Figure 13.3

Morphology of an Enveloped Virus

Figure 13.4

Morphology of a Helical Virus

Figure 13.5

Morphology of a Complex Virus

Taxonomy of Viruses

• Family names end in -viridae.• Genus names end in -virus.• Viral species: A group of viruses sharing the

same genetic information and ecological niche (host). Common names are used for species.

• Subspecies are designated by a number.

Figure 13.6

Growing Viruses• Viruses must be

grown in living cells– Bacteriophages

form plaques on a lawn of bacteria

Figure 13.7

Growing Viruses• Animal viruses

may be grown in living animals or in embryonated eggs

Virus Identification

• Cytopathic effects• Serological tests

– Detect antibodies against viruses in a patient– Use antibodies to identify viruses in neutralization

tests, viral hemagglutination, and Western blot

• Nucleic acids– RFLPs– PCR

The Lytic Cycle

1

2

3

Figure 13.11

4

Figure 13.11

The Lytic Cycle Continued

Figure 13.12

The Lysogenic Cycle

Oncogenic Viruses – Viruses that can induce cancer

• Oncogenic DNA viruses– Adenoviridae– Herpesviridae– Poxviridae– Papovaviridae– Hepadnaviridae

• Oncogenic RNA viruses– Retroviridae– Viral RNA is transcribed to

DNA, which can integrate into host DNA

– HTLV-1 (Human T-cell Lymphotropic Virus; linked to leukemia)

– HTLV-2 (Human T-cell Lymphotropic Virus; linked to hairy cell leukemia)

• Virus remains in asymptomatic host cell for long periods– Cold sores,

shingles

Latent Viral Infections

Figure 13.21

• Disease processes occurs over a long period; generally is fatal– Subacute

sclerosing panencephalitis (measles virus)

Persistent Viral Infections

Figure 13.21

Prions

• Proteinaceous Infectious particle• Inherited and transmissible by ingestion,

transplant, and surgical instruments– Spongiform encephalopathies: Sheep scrapie,

Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome, Kuru, fatal familial insomnia, mad cow disease

Normal Protein vs. Prion

Scrapie

Creutzfeldt-Jakob