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nThe term microbe is short for microorganism which means small organism observed with a microscope

nOver 99% of microbes contribute to the quality of human life

nA small minority cause disease in humans by sheer numbers or producing powerful toxins

nThe major groups of microbes are bacteria, Archaea, algae, fungi, protozoa & viruses

nIn terms of numbers, microbes represent most of the diversity of life on Earth and are found in every

environment.

nProkaryotic single cell with nuclear material but no nuclear membrane or membrane bound organelles

nEukaryotic most cells with organized nucleus and membrane bound organelles

Organelles of

Microbial Origin

nMitochondria and Chloroplasts have DNA similar to that of a Prokaryotic cell and can reproduce

independent of the rest of the Eukaryotic cell.

nIt is believed that both chloroplasts and mitochondria were one independent Prokaryotes who took up

residence in the Eukaryotic cell and have developed a special symbiotic relationship

nMitochondria and Chloroplasts have DNA similar to that of a Prokaryotic cell and can reproduce

independent of the rest of the Eukaryotic cell.

nIt is believed that both chloroplasts and mitochondria were one independent Prokaryotes who took up

residence in the Eukaryotic cell and have developed a special symbiotic relationship

Bacteria

nOnly one cell a prokaryotic cell

nLive in all environments even above boiling point and below freezing point

nBasically three shapes spherical , rod , and spiral or helical (spirullum) Exist as individuals or cluster

together to form pairs, chains, squares, or other groupings

nSome form spores

nSome are photoautotrophic - make their own food as plants and give off oxygen Cyanobacteria are

also aerobic Purple and green bacteria are anaerobic

nSome are chemoautotrophic - synthesize their own food using energy from chemical reactions

important for recycling in nitrogen and sulfur cycles

nSome have flagella - rotates like a tiny outboard motor, others

secrete a slime layer and move over surfaces like slugs

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GRAM + VS. GRAM BACTERIA

Gram positive bacteria

nstain purple under Gram stain

nhave a thick bilayer wall of the polymer peptidoglycan.

Gram negative bacteria

nstain red

nhave a thin layer of this polymer and an additional lipopolysaccharide outer layer, LPS,

noften endotoxic - capable of initiating inflammation and cell-mediated immune responses

ne.g., Salmonella, Shigella, and Escherichia.

Archaea

nSimilar to bacteria prokaryotic

nCell walls lack peptidoglycan + other differences

nOrigin very old - during formation of the earth

n Extremely tolerant to heat, acid, and toxic gases

n Found in extreme habitats in anaerobic environments to produce methane, high salt concentrations or

hot acid environments

nInvolved in carbon & nitrogen cycles, assist in digestion, & can be used in sewage treatment

Algal Protists

(ALGAE)

nAre Eukaryotic

nFound in fresh and salt water environments

nCan live on rocks, trees, and in soils with enough moisture

nCan carry on photosynthesis produce large amount of oxygen

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nDiatoms, Clamydomonas, Volvox, Spirogyra

Animal-like Protists

(PROTOZOA)

nProtozoa means little animal act like tiny animals Eukaryotic

nHunt other microbes for food

nMainly feed on bacteria, also other protozoa and some algae

nDigest food in digestive organelles

nCiliates, Amoebaes, Flagellates - Paramecium, Amoeba, Euglena

nMost are not harmful a few are harmful

nCertain protozoa can cause dysentery and malaria

Fungi

nCellular level, more like animals than plants Eukaryotic

nCant synthesize their own food

nSingle celled as yeast or multicellular clusters as molds & mushroomsnMulticellular ones form filament like strands hyphae

nGrow best in slightly acidic environment can grow in low moisture

nLive in soil, on plants & animals, in fresh & salt water

nOne teaspoon of topsoil has about 120,000 fungi

nBakers yeast for bread and brewing, some are used for antibiotics, others serve as decomposers

nSome cause disease in humans, animals and plants ruin to of fruits & vegetables per year

VIRUSES

nAre acellular

nConsists of a piece of nucleic acid (DNA or RNA) encased in protein and in some cases a membrane-

like envelope

nThey come in many shapes

nFound anywhere there are cells to infest

nExist to reproduce must take over a suitable host cell

nUses the cell machinery of the host cell to reproduce

PRIONS

nproteinaceous infectious particles, associated with a number of diseases

ncharacterized by loss of motor control, dementia, paralysis, wasting and eventually death

nMad Cow Disease in cattle

nCreutzfeld-Jacob disease (CJD) in humans

BENEFICIAL VS HARMFUL MICROBES

nOver 99% contribute to the quality of human life

nLive in every environment on earth

nImportant in ecological systems

nImportant in biogeochemical cycles

nHuman digestion depends upon them

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nImportant to the food industry and the productions of many products

nHelp with wastewater and oil spill cleanup

nSmall minority cause disease

Cysts&Spores

Less resistant resting structures (spores and cysts) are formed by other microbial species.

Spores and cysts are less resistant to harsh treatments than are endospores, but do have some

resistance especially to desiccation.

Endocysts, which are essentially bags within something, are typically one of two different things.

One of which is a bag or layer of cells within an organsims such as an animal that is not generally

associated with normal function. The second, refers to a collection of cells, like free living organisms that

clump together and form a supercolony, or endocyst. These are often seen in certain marine archeae

and cyanobacteria, or corals. This colony is not a germinating spore, or in any way associated with

reproduction, other than its obvious survival advantages to the organism(s) as a whole. Spores on

the other hand are typically self replicating reproductive bodies or non vegitative states of organisms.

The best studied spores are those found in certain types of fungus, bakers yeast (S. cerevisiae) and

Neurospora crassis and bacteria of the bacillus sp. which includes the extremely well studied strain B.

subtilis, and the pathogen B. anthracies, which causes Anthrax. In the case of the yeast, the sporesare differentiated sexually mature progeny that are capable of self replication, but are heartier and

genetically different than the parents, and or a daughter cell, which is the product of a direct replication.

In the bacteria, in response to harsh conditions, they will often form spores, which are a condensed and

protected collection of the cells genetic material that is capable of re-growth upon introduction into a

suitable environment. In the case of Anthrax, this is often in the skin, lungs and tissue of cows.