Microbial nutrition and nutritional requirements 3 rd lecture

Microbial nutrition, and nutritional requirements 3 rd lecture prepared by Dr. Ihsan edan alsaimary Professor department of microbiology – college of medicine – university of basrah - iraq

q. Objectives of the lecture q 1 -define microbial nutrition q 2 - determine the types of nutrients q 3 - classify the microorganisms depend on the types of nutrition q 4 -discuss the importance of each nutrients in the livuiing of microorganisms q 5 - clarify physicochemical factors affecting on microorganisms life

nutrition process by which chemical substances (nutrients) are acquired from the environment and used for cellular activities essential nutrients must be provided to an organism Two categories of essential nutrients: macronutrients micronutrients or trace elements

• macronutrients – required in large quantities – role in cell structure and metabolism – Ex: proteins, carbohydrates • micronutrients or trace elements – required in small amounts – involved in enzyme function and maintenance of protein structure – Ex: manganese, zinc, nickel

Nutrients • Inorganic nutrients – atom or molecule that contains a combination of atoms other than carbon and hydrogen – metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water • Organic nutrients – contain carbon and hydrogen atoms and are usually the products of living things – methane (CH 4), carbohydrates, lipids, proteins, and nucleic acids

Chemical Composition of bacterial Cytoplasm • • 70% water Proteins 96% of cell is composed of 6 elements: – – – Carbon Nitrogen Oxygen Hydrogen Phosphorous Sulfur

The Requirements for Growth • Physical requirements • 1 -temperature, • 2 -p. H • 3 -Oxygen requirement • 4 -osmotic pressure (water) 5 -Hydrostatic pressure 6 -Radiation • Chemical requirements carbon, oxygen, nitrogen, sulfur, phosphorus, trace elements, and organic growth factors

Growth Factors organic compounds that cannot be synthesized by an organism & must be provided as a nutrient such as essential amino acids, vitamins , nitrogen bases, others

Obtaining Carbon • Heterotroph – organism that obtains carbon in an organic form made by other living organisms – proteins, carbohydrates, lipids and nucleic acids • Autotroph – an organism that uses CO 2 (an inorganic gas) as its carbon source – not dependent on other living things

Classification of microorganisms according to carbon sources and energy sources: • Nutritional types – Chemo • Chemical compounds – Photo- Name of group Carbon source Energy source Photoautotrophs ( autotrophs) CO 2 sunlight chemoautotrophs CO 2 Simple inorganic chemicals photoheterotrophs organic sunlight Chemoheterotrophs (Heterotrophs) organic Metabolizing organic cmpds • light

Other Heterotrophs • Saprobes – decompose dead organisms – recycle elements – release enzymes to digest materials • Parasites – utilize tissues and fluids of a living host – cause harm

Environmental Influences on Microbial Growth • • • 1. 2. 3. 4. 5. 6. temperature oxygen requirements p. H Osmotic pressure radiation hydrostatic pressure

1 -Temperature 1. Psychrophiles • optimum temperature below 15 o. C, capable of growth at 0 o. C • Examples are Arthrobacter sp. , Psychrobacter sp. and members of the genera Halomonas, Pseudomonas, Hyphomonas, and Sphingomonas. 2. Mesophiles • • optimum temperature 20 o-40 o. C, EX: most human pathogens 3. Thermophiles • • optimum temperature greater than 45 o. C Ex: Thermus aquaticus

Physiological adaption at High temperaturemodification by thermophiles • Relative greater conc. of guanine & cytosine in DNA & RNA • GC base pair involve in three hydrogen bonds making them more stable at high temperature than AT base pair that form only two hydrogen bond • Stability of DNA & RNA is critical to cell survival • Enzymes thermally stable • high conc. of hydrophobic Amino acid • Cytoplasmic membrane is modified • high proportion of high molecular weight saturated fatty acid.

2 -Oxygen Requirement • molecular oxygen (O 2) as a necessity of life, but it is actually in a sense a poisonous gas • metabolic systems require oxygen for aerobic respiration • Microbes that use molecular oxygen (aerobes) produce more energy from nutrients than microbes that do not use oxygen (anaerobes) • superoxide dismutase (SOD), catalase, hydrogen peroxidase • Enzymes which neutralize toxic oxygen

2. Oxygen Requirements • Aerobe – requires oxygen • Obligate aerobe – cannot grow without oxygen • Facultative anaerobe – capable of growth in the absence OR presence of oxygen • Microaerophile – does not grow at normal atmospheric tensions of oxygen – i. e. , the soil, water or the human body – EX: Helicobacter pylori & Campylobacter & Borrelia

2. Oxygen Requirements • Anaerobe – does not require oxygen – Ex: Clostridium • Capnophiles – Need Higher conc. Of CO 2 – Ex: Erysipelothrix • Aerotolerant anaerobes – does not utilize oxygen but can survive and grow to limited extent in its presence – Ex: Peptostreptococcus & Bateroides

3. p. H • Alkaliphiles – optimum p. H is relatively to highly basic • Ex: Bacillus okhensis & • Alkalibacterium iburiense • Neutrophiles – optimum p. H ranges about p. H 7 (plus or minus) • Ex: human pathogens • Acidophiles – optimum p. H is relatively to highly acidic – Ex: Acidobacterium & Thiobacillus

4 -Osmotic Pressure • Microorganisms obtain almost all their nutrients in solution from the surrounding water • Osmotic pressure – water diffusing across cell membrane in response to solute conc. • Bacteria 80% water • Require water to grow • Xerophiles are extremophilic organisms that can grow and reproduce in conditions with a low availability of water, Xerophiles are often said to be "xerotolerant", meaning tolerant of dry conditions. They can survive in environments with water activity below 0. 8. • Endoliths and halophiles are often xerotolerant. • Ex: Trichosporonoides nigrescens • extreme or obligate halophiles • Adapted to and require high salt concentrations • Ex: Halococcus & Halobacterium

5. Radiation 1 -short wave length , high eneregy radiation 2 -larg wave length , low eneregy radiation • Radioresistance is the property of microorganisms that are capable of living in environments with very high levels of ionizing radiation. ex: Deinococcus radiodurans • Great for killing bacteria • Damages the DNA (making thymine dimers) – in sufficient quantity can kill the organisms – in a lower range causes mutagenesis – Cause melanoma or xeroderma pigmentosa • Spores tend to be resistant – can survive much longer exposures

6. Barophiles(piezophile) • is an organism which thrives at high pressures, such as deep sea bacteria or archaea. They are generally found on ocean floors, where pressure often exceeds 380 atm (38 MPa • Bacteria that grow at moderately high hydrostatic pressures – Oceans • Barotolerants – Grows at pressures from 100 -500 Atm – Ex: Bacillus subtilis • Barophilic – 400 -500 – Ex: Xenophyophores • Extreme barophilic – Higher than 500 – Ex: Halomonas salaria