Kingdom Monera - BacteriaReproduction and Ecological Roles

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Bacterial ReproductionAsexual reproduction: BINARY FISSIONBUDDING

Binary Fission

Most bacterial cells will grow to a fixed size and will then reproduce by binary fission

Note: equal division of cytoplasm and genetic material

1. A single bacterial cell begins to make copies of its genetic material

2. The cell membrane begins to elongate and pulls the genetic material in two different directions

3. The cell membrane grows inward and separates the cells. The cells are genetically identical to one another.

Bacterial cells undergoing different stages of binary fission

Budding

• Results in uneven division of cytoplasm and even division of nuclear material

• More common with fungi, not bacteria

Benefits and disadvantages of sexual and asexual reproduction

Pros ConsAsexual Only 1

organism is necessary-very efficient (20 min life cycle)

Get exact copy (clone) therefore, no species diversity and 1 thing will kill all the bacteria

Sexual Exchange of DNA, therefore high diversity

If there is only 1 individual, it will die with no offspring

Conjugation – Sexual Reproduction A primitive form of sexual reproduction where there is exchange of chromosome (red) material (genetic material) between two bacterial cells through a structure called a pili.

Enlarged

Examples of bacteria that are known to undergo conjugation include: E. coli, Salmonella

Studying bacteria

• Labs use 2 different growth mediums. (substances that bacteria grow in)

Petri dish containing agar

• Bacteria are “streaked” across agar – gelatinous substance made from algae

Innoculating loop used to transfer bacteria to the agar plate

“Slant Test-tube” containing agar with bacteria growing on the surface

Nutrient broth• Nutrient broth

• Test-tubes filled with:• Blood• Beef juice• Other stuff

Ecological Roles of Bacteria• nitrogen fixation in the soil next the roots of some

plants. -plants obtain an easily absorbable form of nitrogen needed for growth.

• degrade some organic compounds -aid in cleaning up oil spills

Beneficial Roles of Bacteria• symbionts in humans and other organisms. • over 1000 types of bacteria in the average

human stomach and intestines that contribute to:

-immunity, vitamin absorption and synthesis, nutrient conversion and fermentation. (probiotic supplements contain many of these bacteria..)

Beneficial Roles of Bacteria

• Used in preparation of fermented foods ex. Yogurt, cheese, soy sauce…

• Used in the study of genetics, molecular biology and biochemistry because of their ability to reproduce so quickly

Some beneficial bacteria

• Escherichia coli – produces vitamin K in large intestine – necessary for blood clotting

• Lactobacillus – yogourt• Streptococcus – to sour milk• Clostridium acetobutylicum – to make

acetone and butanol at an industrial scale

Antibiotics made by bacteria

• Streptomyces – make antibiotics including:• Amphotericin• Kanamycin• Neomycin• Streptomycin• Tetracycline

Harmful bacteria - Pathogenic• Tuberculosis• Meningitis• Botulism• Cholera• Syphilis• Gonorrhea• Diphtheria• Black plague• Gangrene

Treatments for Bacterial Infections

• 1. Antitoxin – to neutralize a chemical made by bacteria that produce toxins

- ie. Botulism• 2. Antibiotics – chemicals produced by

other organisms that kill the bacteria in a form of chemical warfare

- ie. Penicillin (a fungus) makes antibiotics

• 3. disinfectant – to kill all bacteria on surfaces

• 4. antiseptic – to kill most bacteria on the body surface

Other ways to slow down growth or kill bacteria in food

• 1. Keep cold/freeze – slow down metabolism

• 2. Can – keep air out – slows growth – heat kills enzymes

• 3. Dry – take away water – needed for metabolism

• 4. Cure – the salt draws away moisture from the food – the smoking dries the food

• 5. Preservatives – chemicals that kill bacteria

• 6. Salt – draw away moisture• 7. Sugar – draw away moisture

Effective use of antibiotics• Take only when necessary – don’t work on

viruses• Take for total length of time – endospores

(protective coat) forms around bacteria for protection and when the conditions are good again, the bacteria becomes active again

• Take complete dose or else you increase risk of antibiotic resistant bacteria

Antibacterial Agents and Resistance

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Antibiotics

Definition: a substance produced by a microorganism that restricts the growth of another microorganism

Where do antibiotics come from?

• many are produced from other living organisms example. Penicillin is collected from the fungi penicillium (above) Streptomycin comes from the bacteria streptomyces• some antibiotics are modified chemically and some are produced synthetically

Penicillium fungi : produces the antibiotic penicillin

How do antibiotics work? Antibiotics that target a wide

range of bacteria are termed broad spectrum. Those that target a narrow range are termed narrow spectrum.

Some antibiotics actually destroy bacteria (inhibit cell processes) whereas others keep the bacterial cell from reproducing (inhibit binary fission)

Above: Wafers containing antibiotics are placed on an agar plate of bacteria. The cloudy areas show bacterial growth. Circles of poor bacterial growth show that bacteria will not grow in the presence of that antibiotic.

Antibiotic Resistance

As close as possible to 100% of harmful bacteria must be killed off when taking a round of antibiotics. If not, the surviving bacteria will most likely carry genes that are resistant to the initial antibiotic and will then begin to multiply.

Failure to take entire prescribed dosages of antibiotics can lead to the growth of antibiotic resistant bacteria.

When antibiotics are administered when they are not needed we are exposing more bacteria to selection for resistance.

Improper usage and dosaging of antibiotics also contributes to the appearance of resistant bacteria.

NOTE: Remember as well that the genes for antibiotic resistance can also be transferred to other normal bacteria through the conjugation.

Staphylococcus aureus bacteria are one of the types of bacteria normally found existing on human skin surface. They are capable of causing skin infections in those with weakened immune systems. (see picture to left)

Skin infections caused by these bacteria were treated successfully in the 1940’s and 50’s with penicillin. Presently, almost all strains are resistant to penicillin which leaves only a small section of drugs (vancomycin) to treat it.

The picture to the left shows a new form of S.aureous that is beginning to show resistance to vancomycin.

Antiseptics

Definition: Antimicrobial substances that are applied to living tissue (skin) to inhibit the growth of bacteria

• Some destroy bacteria (germicides) and some inhibit the growth of bacteria• Overuse can lead to increased dangerous resistant strains of bacteria

Common Types of AntisepticsAlcohol (surgical alcohol)

– Used to disinfect skin before injections are givenBoric Acid

– Used in yeast infection treatments, cold sore medications, burn cream and eye contact solution (although not very effective)

Chlorhexidine Gluconate– Used in gingivitis treatment

Hydrogen peroxide– Used for cleaning of wounds (although antibacterial soap and water is

actually more effective)Iodine

– Used in pre and post operative cleaning and has a very wide scope of antimicrobial activity

Phenol compounds– Used in pre operative hand washing, mouth washes and throat lozenges

Natural antiseptics– Includes saliva, tears, breast milk and gastric acids

Disinfectants

Definition: antimicrobial agents applied to non-living objects that destroy microorganisms (including bacteria)

• Many disinfectants are harmful (toxic) to humans, animals and the environment

• Overuse can lead to resistant strains of bacteria

Common Types of DisinfectantsAlcohol

• Wide spectrum, highly effective and non-corrosive but are a fire hazard

Oxidizing Agents (ex. Chlorine, peroxide, iodine…)• Destroys the cell membrane of bacteria• Commonly used in

• Bleach, swimming pool cleaners, drinking water treatment…)

UV light• Can be used in dental tool disinfection or for

cleaning any other non-porous surfaces