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Microbio Report 4
Microbial Growth
| Question | Answer |
|---|---|
| refers to the number of cells, not the size of cells | Microbial Growth |
| Growing microbes are increasing in number and accumulates into groups of cells large enough to be seen without microscope | COLONIES |
| True or False. Many bacteria survive and grow slowly | TRUE |
| is a result of cell division in a microbial cell which results from cell division. | GROWTH |
| True or False. In microbiology, growth refers to the increase of a microbial cell IN SIZE , NOT IN NUMBERS. | FALSE |
| the cycle when one cell separates to form two new cells. | Cell generation |
| The time it takes to complete this process for a generation to occur | Generation Time |
| cellular division process that involves elongation of the cell to twice its original size and the formation of a partition which constricts a cell resulting into the formation of two daughter cells. | BINARY FISSION |
| the partition is the result of the cytoplasmic membrane's inward growth | SEPTUM |
| variations in binary fission (2) | (1) can be observed in Bacillus subtilis where a septum forms without cell wall constriction. (2)in budding bacterium Caulobacter where constriction occurs without septum formation. |
| another form of cell division. a process where a single totally new daughter cell forms with the parent cell retaining its identity | BUDDING CELL DIVISON |
| FUNDAMENTAL DIFFERENCE OF BINARY FISSION AND BUDDING | in budding bacteria, the cell wall grows from a single point or polar growth. in a bacteria that undergoes binary fission, it grows throughout the whole cell (intercalary growth) |
| a thick layer of bacterial cells that sticks to each or to the surface. are microbial communities that forms slime or hydrogel that adhere to surface | BIOFILM |
| Bacteria in biofilm communicate through? | QUORUM SENSING |
| When bacterial cell numbers are plotted as arithmetic coordinates as a function of time, a curve with a ____ is obtained. | continuously increasing slope |
| By contrast, when the cell number is plotted on a semilogarithmic graph, the points fall on a _____ line | STRAIGHT LINE |
| a repetitive pattern, where the number of cells doubles in a constant time interval | EXPONENTIAL GROWTH |
| the final cell count after a certain period of time | FINAL CELL NUMBER (N) |
| s the rate at which the population is growing at any instant | INSTANTANEOUS GROWTH RATE CONSTANT (k) |
| Instantaneous Growth Rate is allegedly known as _____ and is the reciprocal of generation time | DIVISION RATE |
| True or False. An organism growing in an enclosed vessel, such as a tube or flask also known as a batch culture, can grow exponentially indefinitely. | FALSE |
| List the Growth Cycle (4) | 1. Lag Phase 2. Exponential Phase 3. Stationary Phase 4. Death Phase |
| It measures the cells in the culture that are capable of reproducing. | VIABLE CELL COUNT |
| It is a quantitative measure of light scattering by a liquid culture, increases with the increase in cell number. | Optical density / Turbidity |
| A microbial culture is inoculated into a fresh media, growth begins only after a period of time , the interval may be brief or extended, depending on the history of the inoculum and the nature of the medium and growth conditions. | LAG PHASE |
| the lag phase occurs because of the following reasons (3) | (1) inoculum is taken from an old culture. (2) Inoculum is of low viability or contains damage cells. (3) transferred from a rich culture medium to a poorer one. |
| the cell population doubles at regular intervals for a brief or extended period. are typically in their healthiest state and are thus most desirable for studies of their enzymes or other cell components. | LOG / EXPONENTIAL PHASE |
| The rate of exponential growth is influenced by ? (3) | temperature, composition of the culture medium. As well as by genetic characteristics of the organism itself. |
| the amount of surface area or total exposed area of a body relative to its volume or size. | SURFACE-TO-VOLUME RATIO |
| True or False. Small cells have an increased capacity for nutrient and waste exchange compared with larger cells, and this metabolic advantage greatly affects their growth and properties. | TRUE |
| In a batch culture, exponential growth cannot be maintained indefinitely. Growth becomes limited in such cultures because either an essential nutrient in the culture medium is depleted or the organism’s waste products accumulate. | STATIONARY PHASE |
| there is no net increase or decrease in cell number and thus the growth rate of the population is zero. | STATIONARY PHASE |
| Two processes that balances each other . ex. some cells in the population grow while others die. | CRYPTIC GROWTH |
| WHY CELLS ENTER STATIONARY PHASE? (3) | (1) . Nutrient Depletion (2) Accumulation of Waste Products (3) Limited Space |
| After stationary phase ,the population will enter the ____ phase of the growth cycle which like the exponential phase, occurs as an exponential function. | DEATH PHASE |
| True or False. Whereas the rate of cell death is much faster than the rate of exponential growth and viable cells cannot remain in a culture for months or even year. | FALSE |
| True or False. the quantity of light dispersed by a cell suspension depends on the size of cells present. | FALSE |
| It provides a quick and common method for assessing cell numbers in the answer. | TURBIDITY MEASUREMENTS |
| It is described as the cloudiness or haziness of a fluid caused by suspended insoluble particles | TURBIDITY |
| is an instrument that measures the unscattered light that passes through a sample, measurements of turbidity are made. | SPECTROPHOTOMETER |
| The unit of turbidity is? | OPTICAL DENSITY |
| It is the state or quality of being clouded, it is a widely used method to determine the cell number of growing microorganisms in a culture, common technique to count the quantity of developing microorganisms | TURBIDITY |
| True or False. Turbidity readings can therefore be used as a substitute for total or viable counting methods. However, before this can be done, a standard curve must be prepared that relates cell number (microscopic or viable count) to turbidity. | TRUE |
| can divide and form offspring, and in most cell-counting situations, these are the cells we are most interested in | VIABLE CELLS |
| A _____ count, also called a ___ count, is used to count the number of viable cells on the agar plate | VIABLE COUNT. PLATE COUNT |
| METHODS FOR VIABLE COUNTS (2) | Spread Plate and Pour Plate |
| A volume (usually 0.1 ml or less) of an appropriately diluted culture is spread over the surface of an agar plate using a sterile glass spreader. t in this method only surface colonies will form. | Spread-plate method |
| A known volume (usually 0.1-1.0 ml) of culture is pipetted into a sterile Petri plate. This method will produce both subsurface and surface colonies. | Pour-plate method |
| Count colonies only on plates that contain between how many colonies? Too many: not form colonies and some colonies to fuse, leading to erroneous measurements o Too little: statistical significance of the calculated count will be low | 30 and 300 colonies |
| To obtain a countable colony number the sample must be _____ due to the fact that the approximate viable count cannot be known ahead of time. | DILLUTION |
| Number of colonies obtained in a viable count depends on: (4) | - inoculum size, viability of the culture, culture medium, incubation conditions |
| same type of specimen is used so that it could result into a synchronous process and uniform colony morphology | PURE CULTURE |
| culture where cells deposited on the plate will not all form colonies at the same rate . Also, the size of the colonies may vary. Tiny colonies may be missed in counting | MIXED CULTURE |
| Plating inconsistencies (4) | -inaccurate pipetting of a liquid sample, a nonuniform sample, insufficient mixing, heat intolerance of specimen if pour plate method is used |
| True or False. plate counts can be highly unreliable when used to assess total cell numbers of natural samples, such as soil and water. | TRUE |
| Why do plate counts reveal lower numbers of cells than direct microscopic counts? | • Microscopic methods o Include count of dead cells • Plate count o Do not include dead cells only viable ones |
| can be done by simply observing and enumerating the cells present by a microscopic cell count whether in a culture or natural sample | TOTAL CELL COUNT |
| can be performed either on samples dried on slides or on liquid samples. | MICROSCOPIC CELL COUNT |
| This type of sample can be stained to increase contrast between cells and their background. | DRIED SAMPLE |
| counting chambers consisting of a grid with squares of known area etched on the surface of a glass slide are used | LIQUID SAMPLE |
| A specially designed slide used in direct microscopic counts | Petroff-Hausser cell counter |
| TRUE OR FALSE. Microscopic counting provides an estimation rather than an exact count due to the limitations of the technique. | TRUE |
| Enumerate the limitations of Microscopic Counting (5) | dead cells cannot be distinguished from live cells, Precision is difficult to achieve, Small cells are hard to detect, Low-density cell suspensions have few cells, Motile cells must be immobilized, Debris in the sample can be mistaken for microbial cell |
| Can stain all cells because it reacts with DNA, was used to determine the number of nuclei and to assess gross cell morphology | DAPI STAIN |
| o differentiates live from dead cells by detecting whether the cytoplasmic membrane is intact or not. | GENERAL FLUORESCENT STAIN |
| can be prepared by attaching fluorescent dyes to specific nucleic acid probes. | Highly specific fluorescent stains |
| target genes encoding enzymes that catalyze specific metabolic processes o a metabolism can be inferred that may reveal the cell’s ecological role in the microbial community. | Other fluorescent probes |
| Most common type of continuous culture that is an open system • A known volume of sterile medium is added at a constant rate while an equal volume of spent culture medium is removed at the same rate | CHEMOSTAT |
| The main container where microbial growth occurs. | CULTURE VESSEL |
| Adds sterile growth medium to the culture vessel at a controlled rate. | INFLOW PUMP |
| Removes spent culture medium and microbial biomass at the same rate as inflow. | OVERFLOW PUMP |
| Ensures even mixing of culture and nutrients for uniform growth. | STIRRING MECHANISM |
| Regulates the rate of medium inflow, controlling specific growth rate. | DILLUTION RATE CONTROLLER / FLOW RATE REGULATOR |
| : Allows periodic sampling for analysis and monitoring. | SAMPLING PORT |
| Maintains optimal environmental conditions for growth. | pH and TEMPERATURE CONTROL |
| Measure parameters like biomass, nutrient levels, and pH. | SENSORS AND MONITORING DEVICES |
| Provides oxygen for aerobic microorganisms if needed | AIR SUPPLY |
| It enables control over both the specific growth rate (k) and growth yield (biomass per ml) of a microbial culture. | CHEMOSTAT |
| Biofilms are for? (2) | Sharing nutrients and sheltering bacteria |
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Biojam
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