1. Department Chemical and FoodInstitute of Technology of Cambodia

2. Abstract Colony= group of bacteria in the only type Phytoplankter = micro –organic live in the water fresh or sea. Bloom = youth

3. Abstract background : growth rate is inversely to body size. Methodology : compare measuring the growth of individual colonies of bloom-forms and size of migro- organisms by using microscopy and digital image ananlysis. result: large intraspecific variation in both the slope of these relationships and in the growth rate of colonies at standard size.

4. I. Introduction Organism size has important relate to mechanisms structuring organisms, population, communities, and whole ecosystems. Where R is physiological rate of interest M is organism mass a,b are scaling constants

5. II.Methods The method for measuring the growth of individual phytoplankton colonies we developed consists of isolating single colonies into wells of a chambered microscope slide and measuring the volume of the colony over time using an image analysis system and a dissecting microscope. Growth rate is then calculated from changes in colony volume over several days.

6. In the first experiment, we quantified growth rate-size relationships for three M. aeruginosa genotypes isolated from three hard-water Michigan lakes that varied widely in trophic status. The M. aeruginosa genotypes have previously been shown to vary in population growth rate in batch culture but it is not clear whether these differences were driven by differences in colony size or other factors that vary across genotypes.

7. We measured colonies under a dissecting microscope using images captured with a digital camera. To calculate colony volume, we needed an estimate of depth for each colony, which we assumed was approximately equal to the width of the colony measured perpendicular to the greatest axial linear dimension near the middle of the colony.

8. Observations of rotated colonies indicated that this approach provided a reasonable approximation of colony depth. We calculated colony volume (mm3) as the product of surface area and depth.

11. For the third experiment: experimental condition and methods for measuring colony volume were the same in the first experiment, except that each genotype was accumated under experimental conditions for 38 days. Colony used in this experiment were selected to be representative of the rang of colony size in each culture.

12. Initial colony size was used for statistical analyses, rather than colony size averaged over the incubation interval, because we wanted to avoid contaminating the independent variable(colony size) with parameters that could be influenced by the dependent variable (growth rate).

14. The first experiment for three M.aeruginosa: Strong negative relationships between growth rate and initial colony size. Slope range= - 1.002 to -0.487 The Hudson genotype having a slope was roughly half of the other.

16. The second experiment for four M.aeruginosa: Slope range= -1.622 to -0.395 There was twice the error around the slope. Found no evidence of bias stemming from size-related resource. Small and large colony grew similarly when grew alone or together.

18. The third experiment for five M.aeruginosa: No overall effect of method on growth rate. Significant different in growth rate among the five genotypes. Statistically different for only HudsonBD02 grew faster as individual colonies.

20. Discussion We found that the growth rate of M.aeruginosa genotype isolated present a wide productivity gradient. The grow rate varied independently of colony size. HudsonBD02, the slope didn’t vary significantly between the two experiment. Obtain similar responses at least one test and that methode should be valuable for other studies measuring the growth of microbes.

21. Hudson grew faster as an isolated colonies than in batch culture. Figure 4. Population and colony growth rate comparison.

22. Given the negative relationship between colony size and grow rate varied in slope. Although the genotypes were relatively similar in shape, colonies of the Hodson genotype tended to contain more voids than the other two genotypeused.

23. Conclusion Colony growth rate decrease with increasing colony diameter Variation of size of phytoplankton is affect to growth rate. Quantify the influence of colony size on growth and their role can make harmful algal blooms.

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