Microbiology - Chapter 4

The first ____ cells appeared 2 to 3 billion years ago

Eukaryotic

_______ all evolved from the Last Common Ancestor

• Bacteria

• Archaea

• Eukarya

First primitive eukaryotes were likely ___-celled and ___

Single, Independent

Aggregated

Forming colonies

Flagella

• Long projections

• Few in number

Cilia

• Short projections

• Numerous

The Glycocalyx is the

Outermost layer that comes into direct contact with the environment

The Glycocalyx is composed of

Polysaccharides

The Glycocalyx appears as

• A network of fibers

• A slime layer

• A capsule

The Glycocalyx contributes to

• Protection

• Adherence

• Signal reception

Most animals lack

Cell walls

___ and ___ do not have cell walls

• Protozoa

• Helminths

Cell walls of fungi

• Rigid and provide structural support and shape

• Different in chemical composition from bacterial and archaeal cell walls

• Thick inner layer of polysaccharide fibers composed of chitin or cellulose

• Thin outer layer of mixed glycans

The Cell Membrane contains

Sterols of various kinds

The Cell Membrane

Typical bilayer of phospholipids in which protein molecules are embedded

Relative rigidity give __ to the membrane

Stability

Important in cells that do not have a cell wall

Sterol

__ of eukaryotes have a similar function as those in bacteria and archaea, serving as selectively permeable barriers

Cytoplasmic membranes

Boundary Structures

• Cell Wall

• Cell Membrane

Nucleus is the

Most prominent organelle of eukaryotic cells

The nucleus separated from the cell cytoplasm by an external boundary called the __

Nuclear envelope

Internal Structures

• Nucleus

• Endoplasmic Reticulum

• Golgi Apparatus

The nucleus is composed of

Two parallel membranes (lipid-bilayers) separated by a narrow space

The nucleus is perforated (series of holes) with

Small, regularly spaced pores, formed at sites where the membranes unite

The nucleus macromolecules

Migrate through the pores to the cytoplasm and vice versa

Endoplasmic Reticulum

A series of membrane tunnels used in transport and storage

Rough endoplasmic reticulum (RER):

• Allows transport materials from the nucleus to the cytoplasm and to the cell’s exterior

• Ribosomes attached to its membrane surface

Smooth endoplasmic reticulum (SER):

• Closed tubular network without ribosomes

• Functions in nutrient processing and in synthesis and storage of nonprotein macromolecules such as lipids

Golgi Apparatus

• The site in the cell in which proteins are modified and then sent to their final destinations

• Always closely associated with the endoplasmic reticulum

Golgi Apparatus consists of

Several flattened, disc-shaped sacs called cisternae

Transitional vesicles

Are picked up at the face of the Golgi apparatus

Condensing vesicles

Pinch off of the Golgi apparatus and are then conveyed to lysosomes or transported outside the cell

Proteins are

Modified within the cisternae by the addition of polysaccharides and lipids

Nature’s Assembly Line

• Nucleus

• Endoplasmic reticulum

• Golgi apparatus

Nature’s Assembly Line Procedure

1. A segment of DNA containing the instructions for producing a protein is copied into RNA, and this RNA transcript is passed out through the nuclear pores directly to the ribosomes on the endoplasmic reticulum

2. Specific proteins on the RER are deposited in the lumen and transported to the Golgi apparatus

3. Proteins in the Golgi apparatus are chemically modified and packaged into vesicles to be used by the cell

Lysosomes

• Bud off the Golgi apparatus as a vesicle

• Contain a variety of enzymes involved in the intracellular digestion of food particles and protection against invading microorganisms

• Participate in the removal of cell debris in damaged tissue

Vacuoles

• Membrane-bound sacs containing fluids or solid particles to be digested, excreted, or stored

• Found in phagocytic cells in response to food and other substances that have been engulfed

• Contents of a food vacuole are digested through a merger of a vacuole with a lysosome

Mitochondria

• Generate energy for the cell

• Composed of a smooth, continuous outer membrane with an inner folded membrane
  Folds on the inner membrane are called cristae

Cristae

• Hold the enzymes and electron carriers of aerobic respiration

• Extracts chemical energy contained in nutrient molecules and stores it in the form of high-energy molecules, or ATP

Mitochondria unique organelles

• Divide independently of the cell

• Contain circular strands of DNA

• Have bacteria-sized 70S ribosomes

Cytoplasm

Substance inside the plasma and outside the nucleus

Cytosol

Fluid portion of cytoplasm

Cytoskeleton are composed of

Microfilaments and intermediate filaments

• gives shape and support

Cytoplasmic streaming

Movement of the cytoplasm throughout a cell

Chloroplasts

• Found in algae and plant cells

• Capable of converting energy from sunlight into chemical energy through photosynthesis

• Produce oxygen gas as a by-product of photosynthesis

• Resemble mitochondria but are larger, contain special pigments, and are more varied in shape

Ribosomes

Distributed throughout the cell

• Scattered freely in the cytoplasm and cytoskeleton

• Attached to the rough endoplasmic reticulum

• Appear inside mitochondria and chloroplasts

Multiple ribosomes are often found arranged in short chains called

Polyribosomes (polysomes)

Ribosomes structure and size

• Large and small subunits of ribonucleoprotein

• Eukaryotic ribosome is 80S, a combination of 60S and 40S subunits

Cytoskeleton functions

• Anchoring organelles

• Moving RNA and vesicles

• Permitting shape changes and movement

Three main types of cytoskeletal elements:

Actin filaments: long, thin protein strands

Intermediate filaments: ropelike structures

Microtubules: long, hollow tubes

Yeasts

• Round to oval shape

• Asexual reproduction, budding

Hyphae

Long, threadlike cells found in the bodies of filamentous fungi

Pseudohypha

• Chain of yeast cells

• Some fungal cells are considered dimorphic and can take either form, depending on growth conditions

Three types of ways “?” can infect humans

• Community

• Hospital

• Opportunistic

Community-acquired infections

Caused by environmental pathogens.

Hospital-associated infections

Caused by fungal pathogens in clinical settings.

Opportunistic infections

Caused by low-virulence species infecting already-weakened individuals.

Harmless spores can cause ____ infections in AIDS patients.

Opportunistic

Fungal cell walls give off ____ that can trigger allergies.

Chemical substances

A number of species are pathogenic to

• Corn

• Grain

__% of yearly fruit crop is consumed by fungi.

40

Heterotrophic

Acquire nutrients from a wide variety of organic substrates

Saprobic

These substrates from the remnants of dead plants and animals in soil or aquatic habitats

Parasitic

Grow on the bodies of living animals or plants, although very few require a living host

Fungi ___ the substrate and secrete enzymes that reduces it to small molecules that can be absorbed by the cells.

Penetrate

Fungi are often found in ___ or adverse environments, and those with high salt or sugar content.

Nutritionally poor

Cells of most microscopic fungi grow in

• Loose Associations

• Colonies

Colonies of yeasts are much like bacteria: they have a

Soft, uniform texture and appearance

Colonies of filamentous fungi are noted for the striking

Cottony, hairy, or velvety texture

Mycelium

The woven, intertwining mass of hyphae that makes up the body or colony of a mold

Septa

The nature of the septa varies from solid partitions with no communication between the compartments to partial walls with small pores that allow the flow of organelles and nutrients between adjacent compartments

Nonseptate hyphae consist of

One long continuous cell

Vegetative hyphae are responsible for the visible ___ that appears on a substrate

Mass of growth

Reproductive, or fertile, hyphae produce

Spores

Spores

• Primary reproductive mode of fungi

• Can be dispersed through the environment by air, water, and living things

• Will germinate upon finding a favorable substrate and produce a new fungus colony in a short time

Asexual Spore Formation

• Sporangiospores

• Conidiospores or conidia

Sporangiospores

Formed by successive cleavages within a saclike head called a sporangium, which is attached to a stalk, the sporangiophore

Conidiospores or conidia

Free spores not enclosed by a spore-bearing sac

The Protozoa

• Name comes from the Greek for “first animals”

• Most are harmless, free-living inhabitants of water and soil

Protozoa contains

All of the major eukaryotic organelles

Cytoplasm divided into two parts

• Ectoplasm

• Endoplasm

Ectoplasm

Clear outer layer involved in locomotion, feeding, and protection

Endoplasm

Granular inner region housing the nucleus, mitochondria, and food and contractile vacuoles

Protozoa Function

• Cell membrane regulates food, wastes, and secretions

• Cell shape can remain constant (as in most ciliates), or change constantly (as in amoebas)

• Size of most protozoans range from 3 to 300 μm:

Protozoa Nutrional and Habitat Range

• Heterotrophic, require food in a complex organic form

• Free-living species scavenge dead plant or animal debris or graze on bacteria and algae

• Some have special feeding structures, such as oral grooves

• Some absorb food directly through the cell membrane

• Pathogenic species may live on the fluids of their host, such as plasma and digestive juices, or actively feed on tissues

• Main limiting factor is availability of moisture

• Predominant habitats are fresh and marine water, soil, plants, and animals

• Can survive in extremes of temperature and pH

Trophozoite

Motile feeding stage requiring ample food and moisture to stay active

Cyst

• Dormant, resting stage when conditions in the environment become unfavorable

• Resistant to heat, drying, and chemicals • Can be dispersed by air currents

• Important factor in the spread of disease

All protozoa reproduce by

• Asexual mitotic cell division

• Multiple fission

___ also occurs in most protozoa

Sexual reproduction

Ciliates participate in conjugation in which two cells fuse and exchange micronuclei

This results in new and different genetic combinations that can be advantageous in

Evolution

Helminths

• Include tapeworms, flukes, and roundworms

• Adult specimens are usually large enough to be seen with the naked eye

• Not all flatworms and roundworms are parasites; many live free in soil and water

• Disease-causing helminths spend part of their lives in the gastrointestinal tract

Flatworms (phylum Platyhelminthes)

• Very thin, often segmented body plan

• Divided into cestodes (tapeworms) and trematodes (flukes)

Roundworms (phylum Aschelminthes)

• Also called nematodes

• Elongated, cylindrical, unsegmented body

In pathogenic helminths, the most developed organ is the

Reproductive tract

Worms have a

A reduction in the digestive, excretory, nervous, and muscular systems

Helminths Life Cycle and Reproduction

• Complete life cycle includes the fertilized egg, larval, and adult stages

• Adults derive nutrients and reproduce sexually in a host’s body

Nematodes

Sexes are separate and different in appearance

Trematodes

Sexes can be separate or hermaphroditic

Cestodes

Generally hermaphroditic (same sexes)

__ is an intermediate that experiences no parasitic development

Transport host