12 The Eukaryotes: Fungi, Algae, Protozoa, and Helminths

Eukaryotic Aerobic or facultatively anaerobic Chemoheterotrophic Most are decomposers Mycology is the study of fungi

The Fungi

Mycology: The Study of Fungi

Table 12.2

Fungi

Table 12.1

Molds

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

Figure 12.2

Yeasts

Unicellular fungi Fission yeasts divide symmetrically Budding yeasts divide

asymmetrically

Figure 12.3

Dimorphism Pathogenic

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

Figure 12.4

Fungal Life Cycle

Figure 12.7

Fungal Diseases (Mycoses) Systemic mycoses: Deep within body Subcutaneous mycoses: Beneath the skin Cutaneous mycoses: Affect hair, skin, and

nails Superficial mycoses: Localized, e.g., hair

shafts Opportunistic mycoses: Caused by normal

microbiota or environmental fungi

Asexual Spores Sporangiosphore Conidiospore

Arthrospore Blastoconidium

Chlamydospore

Figure 12.1

Conidiospores

Figure 12.5a–c

Sexual Reproduction

Plasmogamy: Haploid donor cell nucleus (+) penetrates cytoplasm of recipient cell (–).

Karyogamy: + and – nuclei fuse. Meiosis:Diploid nucleus produces

haploid nuclei (sexual spores).

Sexual Spores Zygospore: Fusion of haploid cells

produces one zygospore.

Figure 12.6

Sexual Spores Ascospore: Formed in a sac (ascus).

Figure 12.7

Sexual Spores Basidiospore: Formed externally on a

pedestal (basidium).

Figure 12.8

Zygomycota Conjugation fungi Coenocytic Produce sporangiospores and zygospores

Rhizopus, Mucor (opportunistic, systemic mycoses)

Zygomycete Life Cycle

Figure 12.6

Ascomycota Sac fungi Septate Produce ascospores and frequently

conidiospores. Aspergillus (opportunistic, systemic mycosis) Blastomyces dermatitidis, Histoplasma

capsulatum (systemic mycoses) Microsporum, Trichophyton (cutaneous

mycoses)

Ascomycete Life Cycle

Figure 12.7

Basidiomycota Club fungi Septate Produce basidiospores and sometimes

conidiospores. Cryptococcus neoformans (systematic mycosis)

Basidiomycete Life Cycle

Figure 12.8

Anamorphs Teleomorphic fungi

Produce sexual and asexual spores. Anamorphic fungi

Produce asexual spores only. rRNA sequencing places most in Ascomycota; a few

are Basidiomycota. Penicillium Sporothrix (subcutaneous mycosis) Stachybotrys, Coccidioides, Pneumocystis (systemic

mycoses) Candida albicans (Cutaneous mycoses)

Fungi Positive Effects Negative Effects

Saccharomyces Bread, wine, beer Food spoilage

Trichoderma Cellulose used for juices and fabric

Cryphonectria parasitica (chestnut blight)

Taxomyces Taxol production Ceratocystis ulm (Dutch elm disease)

Entomorphaga Gypsy moth control

Economic Effects of Fungi

Lichens Mutualistic combination of an alga (or

cyanobacterium) and fungus. Alga produces and secretes

carbohydrates; fungus provides holdfast.

Lichens

Figure 12.10

Eukaryotic Unicellular, filamentous, or multicellular

(thallic) Most are photoautotrophs

The Algae

Algae

Table 12.1

Figure 12.11a

Algae

Dinoflagellata 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

13Viruses, Viroids, and Prions

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

Viruses

Viruses

Figure 13.1

Helical Viruses

Figure 13.4a–b

Polyhedral Viruses

Figure 13.2a–b

Enveloped Viruses

Figure 13.3

Complex Viruses

Figure 13.5a

Viral Taxonomy 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.

Viral Taxonomy Herpesviridae Herpesvirus Human herpes virus

HHV-1, HHV-2, HHV-3

Retroviridae Lentivirus Human

immunodeficiency virus HIV-1, HIV-2

Growing Viruses Viruses must

be grown in living cells. Bacteriophage

s form plaques on a lawn of bacteria.

Figure 13.6

Growing Viruses Animal viruses

may be grown in living animals or in embryonated eggs.

Figure 13.7

Growing Viruses

Animal and plants viruses may be grown in cell culture. Continuous cell lines may be maintained

indefinitely.

Figure 13.8

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

Virus Identification

Figure 13.9

Multiplication of Bacteriophages (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.

1

2

3

Figure 13.11, steps 1–3, 6–7

4

Figure 13.11, steps 4–5, 8

One-Step Growth Curve

Figure 13.10

Lytic cycle: Phage causes lysis and death of host cell.

Lysogenic cycle: Prophage DNA incorporated in host DNA.

The Lysogenic Cycle

Figure 13.12

2

3

4

5

6

Specialized Transduction

Figure 13.13

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.

Attachment, Penetration, and Uncoating

Pinocytosis

Figure 13.14a

Attachment, Penetration, and Uncoating Fusion

Figure 13.14b

Release of an Enveloped Virus by Budding

Figure 13.20

Multiplication of DNA Virus

Figure 13.15

DNA and RNA Viruses Compared DNA: Cellular enzyme transcribes viral

DNA in nucleus. DNA, reverse transcriptase: Cellular

enzyme transcribes viral DNA in nucleus; reverse transcriptase copies mRNA to make viral DNA.

RNA, + strand: Viral RNA is a template for synthesis of RNA polymerase.

DNA and RNA Viruses Compared

RNA – strand: Viral enzyme copies viral RNA to

make mRNA in cytoplasm.

RNA, double-stranded: Viral enzyme copies –

strand RNA to make mRNA in cytoplasm.

RNA, reverse transcriptase: Viral enzyme copes

viral RNA to make DNA in cytoplasm.

Cancer

Activated oncogenes transform normal cells into cancerous cells.

Transformed cells have increased growth, loss of contact inhibition, tumor specific transplant and T antigens.

The genetic material of oncogenic viruses becomes integrated into the host cell's DNA.

Oncogenic Viruses Oncogenic DNA

viruses Adenoviridae Heresviridae Poxviridae Papovaviridae Hepadnaviridae

Oncogenic RNA viruses

Retroviridae Viral RNA is

transcribed to DNA which can integrate into host DNA

HTLV 1 HTLV 2

Latent viral infections Virus remains in asymptomatic

host cell for long periods. Cold sores, shingles

Presistent viral infections Disease processes occurs over

a long period; generally is fatal. Subacute sclerosing

panencephalitis (measles virus)

Figure 13.21

PLAY Animation: Prion Reproduction

Prions

Infectious proteins

Inherited and transmissible by ingestion, transplant, and

surgical instruments

Spongiform encephalopathies: Sheep scrapie, Creutzfeldt-

Jakob disease, Gerstmann-Sträussler-Scheinker syndrome,

fatal familial insomnia, mad cow disease

PrPC: Normal cellular prion protein, on cell surface

PrPSc: Scrapie protein; accumulates in brain cells forming

plaques

Some Plant Viruses

Table 13.6

Single-stranded DNA, nonenveloped viruses Parvoviridae

Human parvovirus Fifth disease Anemia in

immunocompromised patients

Table 13.2 (1 of 20)

Virus Families

Double-Stranded DNA, Nonenveloped Viruses

Mastadenovirus Respiratory

infections in humans

Tumors in animals

Table 13.2 (2 of 20)

Double-Stranded DNA, Nonenveloped Viruses

Papillomavirus (human wart virus)

Polyomavirus Cause tumors;

some cause cancer

Table 13.2 (3 of 20)

Double-Stranded DNA, Enveloped Viruses Orthopoxvirus

(vaccinia and smallpox viruses)

Molluscipoxvirus Smallpox Molluscum

contagiosum Cowpox

Table 13.2 (4 of 20)

Double-Stranded DNA, Enveloped Viruses Simplexvirus (HHV1 and

HHV 2) Varicellavirus (HHV 3) Lymphocryptovirus (HHV

4) Cytomegalovirus (HHV 5) Roseolovirus (HHV 6) HHV 7 Kaposi's sarcoma (HHV 8)

Some herpesviruses can remain latent in host cells.

Table 13.2 (5 of 20)

Double-Stranded DNA, Enveloped Viruses

Hepadnavirus (Hepatitis B virus) Use reverse

transcriptase to produce DNA from mRNA.

Table 13.2 (6 of 20)

Single-Stranded RNA, + Strand, Nonenveloped

Enterovirus Enteroviruses

include poliovirus and coxsackievirus.

Rhinovirus Hepatitis A virus

Table 13.2 (7 of 20)

Single-Stranded RNA, + Strand, Nonenveloped

Hepatitis E virus Norovirus causes

gastroenteritis.

Table 13.2 (8 of 20)

Single-Stranded RNA, + Strand, Enveloped Alphavirus

Alphaviruses are transmitted by arthropods; include EEE, WEE.

Rubivirus (rubella virus)

Table 13.2 (9 of 20)

Single-Stranded RNA, + Strand, Enveloped Arboviruses can

replicate in arthropods; include yellow fever, dengue, SLE, and West Nile viruses

Hepatitis C virus

Table 13.2 (10 of 20)

Single-Stranded RNA, + Strand, Enveloped

Coronavirus Upper respiratory

infections SARS

Table 13.2 (11 of 20)

Single-Stranded RNA, – Strand,

One RNA Strand Vesiculovirus Lyssavirus (rabies

virus) Cause numerous

animal diseases

Table 13.2 (12 of 20)

Single-Stranded RNA, – Strand,

One RNA Strand Filovirus

Enveloped, helical viruses

Ebola and Marburg viruses

Table 13.2 (13 of 20)

Single-Stranded RNA, – Strand,

One RNA Strand Paramyxovirus Morbillivirus Paramyxovirus

Parainfluenza Mumps Newcastle disease

Table 13.2 (14 of 20)

Single-Stranded RNA, – Strand,

One RNA Strand Hepatitis D virus

Depends on coinfection with Hepadnavirus

Table 13.2 (15 of 20)

Single-Stranded RNA, – Strand,

Multiple RNA Strands Influenzavirus (Influenza viruses A and B)

Influenza C virus Envelope spikes can

agglutinate RBCs.

Table 13.2 (16 of 20)

Crossing the Species Barrier

UN 13.3

Single-Stranded RNA, – Strand,

Multiple RNA Strands Bunyavirus (CE virus) Hantavirus

Table 13.2 (17 of 20)

Single-Stranded RNA, – Strand,

Multiple RNA Strands Arenavirus

Helical capsids contain RNA-containing granules

Lymphocytic choriomeningitis

VEE and Lassa Fever

Table 13.2 (18 of 20)

Single-Stranded RNA, Two RNA Strands, Produce DNA

Lentivirus (HIV) Oncogenic viruses

Use reverse transcriptase to produce DNA from viral genome.

Includes all RNA tumor viruses

Table 13.2 (19 of 20)

Double-Stranded RNA, Nonenveloped

Reovirus (Respiratory Enteric

Orphan) Rotavirus

Mild respiratory infections and gastroenteritis

Colorado tick fever

Table 13.2 (20 of 20)