1. how does water behave differently at the scale of bacteria? What are ways the

ID: 82685 • Letter: 1

Question

1. how does water behave differently at the scale of bacteria? What are ways they can overcome this effect

MULTIPLE CHOICE

2. Redox potential affects anaerobic metabolic activity by a) allowing all forms of anaerobic metabolic activity when O2 is not present b) allowing all forms of anaerobic metabolic activity when O2 is present c) allowing all forms of anaerobic metabolic activity at higher temperatures d) allowing more kinds of anaerobic metabolic activity as E0 of the electron donor becomes more negative

3) CO2 is the end product of TCA in aerobic respiration. CO2 can then be used in autotrophy and what in zones where microbial hydrogen production is supported. a) chemoheterotrophy b) organotrophy c) fermentation d) as a terminal electron acceptor e) reverse TCA

4) The activation energy of a reaction that occurs spontaneously is decreased by an enzyme via a) coenzymes b) allosteric sites c) protein rigidity d) precise fit and charge e) none of the above

Explanation / Answer

Bacteria ; common noun bacteria, singular bacterium) constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste,and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals.

Cellular structure :

Intracellular structures

The bacterial cell is surrounded by a cell membrane (also known as a lipid, cytoplasmic or plasma membrane). This membrane encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. As they are prokaryotes, bacteria do not usually have membrane-bound organelles in their cytoplasm, and thus contain few large intracellular structures.

Extracellular structures :

Further information: Cell envelope

In most bacteria, a cell wall is present on the outside of the cell membrane. The cell membrane and cell wall comprise the cell envelope. A common bacterial cell wall material is peptidoglycan (called "murein" in older sources), which is made from polysaccharide chains cross-linked by peptides containing D-amino acids.Bacterial cell walls are different from the cell walls of plants and fungi, which are made of cellulose and chitin, respectively.

Nutritional types in bacterial metabolism

Nutritional type

Source of energy

Source of carbon

Examples

Phototrophs

Sunlight

Organic compounds (photoheterotrophs) or carbon fixation (photoautotrophs)

Cyanobacteria, Green sulfur bacteria, Chloroflexi, or Purple bacteria

Lithotrophs

Inorganic compounds

Organic compounds (lithoheterotrophs) or carbon fixation (lithoautotrophs)

Thermodesulfobacteria, Hydrogenophilaceae, or Nitrospirae

Organotrophs

Organic compounds

Organic compounds (chemoheterotrophs) or carbon fixation (chemoautotrophs)

Bacillus, Clostridium or Enterobacteriaceae

Protecting against food spoilage.

In 1953, W J Scott established that water activity activity is the key to determining if microorganisms will grow. Since yeast, molds and bacteria require a certain amount of available water to support growth, designing a product with an aw below 0.6 provides an effective control. Water activity is defined as the equilibrium relative humidity (ERH) divided by 100. Some common spoilage organisms and their aw limits are listed in Table.

Water activity is a better index for microbial growth than water content.

Water activity better predicts the growth of microorganisms because microorganisms can only use "available" water, which differs considerably depending on the solute. On average, ions bind the most water, whereas polymers bind the least water; sugars and peptides fall into an intermediate position. At the same molecular concentration, salt lowers the water activity more than sugar.

When a substance is added to lower water activity, the result can be complicated. Ideally, an inert material could be added which would decrease water activity without any other effects such as increased ionic strength and decreased surface tension. In reality, the choice of substance can have a profound effect.

Things to Remember

Treatment :

Boiling can be used as a pathogen reduction method that should kill all pathogens. Water should be brought to a rolling boil for 1 minute. At altitudes greater than 6,562 feet (greater than 2000 meters), you should boil water for 3 minutes.

Filtration can be used as a pathogen reduction method against most microorganisms, depending on the pore size of the filter, amount of the contaminant, particle size of the contaminant, and charge of the contaminant particle. Manufacturer’s instructions must be followed. More information on selecting an appropriate water filter can be found at http://www.cdc.gov/parasites/crypto/gen_info/filters.html(https://www.cdc.gov/parasites/crypto/gen_info/filters.html). Only filters that contain a chemical disinfectant matrix will be effective against some viruses.

Disinfection can be used as a pathogen reduction method against microorganisms. However, contact time, disinfectant concentration, water temperature, water turbidity (cloudiness), water pH, and many other factors can impact the effectiveness of chemical disinfection. The length of time and concentration of disinfectant varies by manufacturer and effectiveness of pathogen reduction depends on the product. Depending on these factors, 100% effectiveness may not be achieved. Manufacturer’s instructions must be followed.

If boiling water is not possible, a combination of filtration and chemical disinfection is the most effective pathogen reduction method in drinking water for backcountry or travel use. Manufacturer’s instructions must be followed.

Other treatment methods can be effective against some of the above pathogens:

Ultraviolet Light (UV Light) can be used as a pathogen reduction method against some microorganisms. The technology requires effective prefiltering due to its dependence on low water turbidity (cloudiness), the correct power delivery, and correct contact times to achieve maximum pathogen reduction. UV might be an effective method in pathogen reduction in backcountry water; there is a lack of independent testing data available on specific systems. Manufacturer’s instructions must be followed.

MIOX® systems use a salt solution to create mixed oxidants, primarily chlorine. Chlorine has a low to moderate effectiveness in killing Giardia, and a high effectiveness in killing bacteria and viruses. Manufacturer’s instructions must be followed.

Important: Water that has been disinfected with iodine is NOT recommended for pregnant women, people with thyroid problems, those with known hypersensitivity to iodine, or continuous use for more than a few weeks at a time.

Sanitation

In addition to using the appropriate drinking water treatment methods listed above, you can also protect yourself and others from waterborne illness in the backcountry or while traveling by paying attention to good sanitation practices:

Burying human waste 8 inches deep and at least 200 feet away from natural waters.

Practicing good personal hygiene. Wash hands before handling food, eating, and after using the toilet.

The activation energy of a reaction that occurs spontaneously is decreased by an enzyme protein rigidity.