Micro - growth and metabolism

What are the different ways bacteria can divide?

• Divide into equal or unequal products

• Equal products: binary fission

• Unequal products: simple budding, budding from hyphae, division of stalked organisms, polar growth without size differentiation

What are the cellular level facilitators?

• MreB (actin homologue)

• FtsZ (tubulin homologue)

• Min system

How does MreB facilitate growth and division?

• Bacterial cytoskeleton protein

• Elongation growth by incorporation of new cell wall material along the longitudinal axis

How does FtsZ facilitate growth and division?

• Cytokinesis ring

• Fundamental element of septum formation, constriction and cell division

• Highly conserved across all bacterial species

How does the Min system facilitate division in a bacterium?

• Midcell selection

• Robust positioning of FtsZ at the midcell

• Ensures only midcell divisions over the lifetime of each cell

How does subcellular movement ensure the correct location of division facilitators?

• MreB has rotation along the inner membrane that is directly coupled to cell wall synthesis

• FtsZ is a dynamic midcell ring that spontaneously forms treadmilling rings

• MinC prevents FtsZ from polymerising at the poles by a higher temporal concentration

How does cell division vary between the different types of bacterial species?

• Gram + : no cell wall constriction during or after cell division, daughter cell separation occurs later through autolysins

• Gram - : septum formation causes cell division

What are the main factors that determine growth in a culture?

• Availability of nutrients

• Presence or absence of oxygen

• Temperature

What are the different growth phases of bacteria?

• Lag phase

• Exponential phase

• Stationary phase

• Death phase

What are the different types of bacteria in terms of oxygen usage?

• Obligate aerobes: only grow aerobically

• Aerotolerant aerobes: able to grow both aerobically and anaerobically

• Facultative aerobes: prefer to grow aerobically but can partially grow anaerobically

• Microaerophiles: grow at the interface of aerobic and anaerobic but able to grow better under anaerobic conditions

• Anaerobes: cannot grow in the presence of oxygen

What are the different types of bacteria in terms of temperature?

• Psychrophile: 0-10 degrees

• Mesophile: 10-45 degrees

• Thermophile: 40-70 degrees

• Hyperthermophile: 65-115 degrees

What are the main nutritional classes of bacteria?

• Photolithoautotroph: uses CO2 for carbon, light for energy, inorganic electron donors

• Photoorganoheterotroph: uses organic carbon, light for energy, organic electron donors

• Chemolithoautotroph: uses CO2 for carbon, inorganic chemicals for energy, inorganic electron donors

• Chemoorganoheterotroph: uses organic carbon, organic chemicals for energy, organic electron donors

How do bacteria use fermentation to respire?

• Occurs when there is no oxygen as a terminal electron acceptor

• An organic compound is both the electron donor and acceptor

• Fermentation is an inefficient process

• Only produces 2 ATP molecules through surface-level phosphorylation

• NADH is recycled by reducing pyruvate to lactate and other products such as ethanol

• If only lactate is formed the process is homofermentative

• If other mixed products are formed the process is heterofermentative

How can bacteria be identified by their metabolism?

Use an API strip