Kingdom Monera – Bacteria Characteristics and Diversity

Bacteria were first identified in 1677 by Antonie van Leeuwenhook after he developed a primitive version of the compound microscope. He originally called all single celled organisms he had discovered “animalcules” and they were later separated into groups, one of which included bacteria.

Bacteria are found in three distinct shapes 1.Rod shaped termed: Bacilli Some bacilli have adapted to survival during unfavorable conditions by forming dormant or resting cells called endospores which are resistant to severe physical and chemical stresses. Endospores are a core of DNA that is surrounded by an impenetrable layer. They can last for millions of years and are capable of causing some serious diseases: ex. Anthrax (Bacillus anthraxis) & Tetanus (Clostridium tetani)

2. Spherical shaped Can be found as single cocci, chains, or clumps termed: Coccus Diploids – pairs of spherical shaped bacteria ex. Neisseria (can cause gonorrhea, bacterial meningitis & septicemia) Chains of spherical shaped bacteria (Strepto) ex. Streptococcus ( cause a variety of human disease including meningitis, flesh eating disease, and bacterial pneumonia) Clusters of spherical shaped bacteria (Staphlo) ex. Staphylococcus aureous (can cause a variety of human infections including skin infections, Toxic Shock Syndrome, meningitis….) Staphylococcus aureous

3. Spiral shaped Actually are a form of rod shaped bacteria Termed Spirilla Leptospirillum

Bacterial Structure Example: bacillus structure

Bacterial Cell Structure Internal Surrounded by a cell membrane Single ring of genetic material (chromosome) encased in a nucleoid External Cell Wall Composed of peptidoglycan (as opposed to cellulose in plant cells) Two types Gram positive – have a thick cell wall Gram negative – have a thin cell wall and most bacteria fall into this category Important in antibiotic use as antibiotics affect the ability to produce a cell wall Flagella Used for motility and are driven by energy Can be found alone, at each end, in clusters at the poles or all over the cell Pili (sing. Pilus) Primitive Sexual reporduction Used for transferring genetic material between cells

Methods of Movement 1.Flagella – rotates and driven by energy at the base 2.Bacterial gliding –mechanism that includes ejection of slime and movement of the pili 3.Twitching motility – special pili are used as a hook that is extended repeatedly and used to pull the bacterium along 4.Changes of buoyancy –produce internal gas vesicles (pockets) that they use to regulate buoyancy in the water to find food and light E.coli

Bacteria have recently been classified by the environment that they live in 1.Archaebacteria – live in an environment without oxygen 2. Eubacteria – live in an environment with oxygen Bacteria can also be grouped according to their type of respiration 1.Obligate aerobes – must have oxygen to survive 2.Obligate anaerobes – can only grow in the absence of oxygen 3.Facultative anaerobes – prefer environments with oxygen but can live in environments without oxygen

Nutrition: How do bacteria get the food and energy they need to survive? Some are autotrophs (make their own food) Photosynthetic - use of light for energy Chemosynthetic – use of chemical substances for energy Some are heterotrophs (obtain food from other sources) Saprophytic (obtain raw materials from dead and decomposing matter) Parasitic Symbiotic / mutualistic (ex. Bacteria in the human colon) Chemoheterotrophs: must take in organic compounds for energy and carbon Photoheterotrophs: make their own energy via photosynthesis but must take in organic compounds for carbon

A few bacteria that cause human disease Salmonella bacteria (red) : causes Salmonella poisoning E.Coli bacteria Helicobacter pylori: can cause ulcers, stomach cancer… Tetanus bacteria

Modes of Bacterial disease transmission Direct contact Airborne droplets Bacterial toxins in food (ingestion) Fecal contamination of food Water Vector bites (ex. Mosquito)

Kingdom Monera - Bacteria Kingdom Monera - Bacteria Reproduction and Ecological Roles

Bacterial Reproduction Bacteria reproduce by a process known as BINARY FISSION, a form of asexual reproduction “Splitting into two” Sexual reproduction via a process called CONJUGATION is not common but does occur. Genetic material is exchanged between cells.

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

Binary Fission Animation

Bacterial cells undergoing different stages of binary fission

Conjugation A primitive form of sexual reproduction where there is exchange of chromosome 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

Ecological Roles of Bacteria Certain mutualistic bacteria carry out **nitrogen fixation** in the soil next the roots of some plants. This allows plants to obtain an easily absorbable form of nitrogen needed for growth. Bacteria can be used to degrade some organic compounds therefore can be used to aid in cleaning up oil spills Can be used in the place of harmful pesticides and leave little to no effect on the environment

Beneficial Roles of Bacteria Bacteria are found as symbionts in humans and other organisms. There are 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..) 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 Used for making medicines (Insulin)

Antibacterial Agents and Resistance

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 Failure to take entire prescribed dosages of antibiotics can lead to the growth of antibiotic resistant bacteria. Improper usage and dosaging of antibiotics also contributes to the appearance of resistant bacteria.

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 pictures to left)

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

Common Types of Antiseptics Alcohol (surgical alcohol) –Used to disinfect skin before injections are given Boric 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 Disinfectants Alcohol Wide spectrum, highly effective and non-corrosive but are a fire hazardWide spectrum, highly effective and non-corrosive but are a fire hazard Oxidizing Agents (ex. Chlorine, peroxide, iodine…) Destroys the cell membrane of bacteriaDestroys the cell membrane of bacteria Commonly used inCommonly used in Bleach, swimming pool cleaners, drinking water treatment…)Bleach, swimming pool cleaners, drinking water treatment…) UV light Can be used in dental tool disinfection or for cleaning any other non-porous surfacesCan be used in dental tool disinfection or for cleaning any other non-porous surfaces