Saddleback Journal of Biology - Saddleback College

Fall 2009 Biology 3A Abstracts
8. THE EFFECT OF PH ON HETEROCYSTS IN CYANOBACTERIUM Anabaena sp.
Saman Hashemi. Department of Biological Sciences, Saddleback College, Mission Viejo, CA,
92692, USA
Anabaena are filamentous, colonial cyanobacteria known as blue-green algae that contain two
types of cells: vegetative cells and heterocyst cells. The optimum pH level of Anabaena is
slightly basic to around pH of 8 and is inhibited completely below pH of 5. This research focused
on the effects of heterocyst cell formation during different pH levels. The Anabaena exposed to
higher pH is expected to form more heterocyst cells compare to the lower, more acidic, pH. To
test this hypothesis, two groups of Anabaena were placed in nutrient rich bottled water with pH’s
5 and 8. Then the bacteria were monitored daily in order to maintain the pH of the solutions
indoors for a week. A primary and final count of heterocysts was examined under a microscope
at 400x and the contents of the formation growth of the Anabaena were verified to see if the pH
had affected the heterocysts. Average percent change of heterocysts in acidic solution was -7.05
± 1.61% (± se), n = 3. Average percent change of heterocysts in basic solution was -0.42 ±
0.23% (± se), n = 3. There is a significant percent change of heterocysts between the acidic and
basic solution (p=0.028, one-tailed t-test). Thus my results support my hypothesis that Anabaena
lives more optimal in a slightly basic environment.
9. ANTIBACTERIAL PROPERTIES OF ALCOHOL AND NON-ALCOHOL BASED HAND
SANITIZERS. Maral Iftekhary and Sophia Iribarren. Department of Biological Sciences,
Saddleback College, Mission Viejo, CA, 92692, USA
Hand sanitizers are commonly used by adults and children. The purpose of this experiment
was to test several hand sanitizers and promote public awareness of faulty labels that claim to
eliminate 99.9% of bacteria. Ten Saddleback College students were used to test the different
hand sanitizers containing 60%, 65%, 70% alcohol and 0.13% benzalkonium chloride as active
ingredients. Bacteria colonies were counted to determine and compare the efficiency of nonalcohol
and alcohol based hand sanitizers. The average number of bacteria before the usage of
hand sanitizers was 35 ± 9.73 (±se). The average number of bacteria left after the usage of the
various types of hand sanitizers was 10.3 ± 3.31 (±se).The hand sanitizers with 70% alcohol
eliminated 87% of bacteria; 65% alcohol eliminated 84%of bacteria; 60% alcohol eliminated
79% of bacteria; 0.13% benzalkonium chloride eliminated 66% of bacteria and water eliminated
76% of bacteria. The obtained data was not sufficient to support the hypothesis that 99.9% of
bacteria could be eliminated using the various types of hand sanitizers. Based on results
generated it is recommended to use hand sanitizers with at least 70% alcohol as an active
ingredient to eliminate the most bacteria.
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Saddleback Journal of Biology
Spring 2010