Alcaligenes Eutrophus and Its Role in Biodegradable Polymer Production: Difference between revisions

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<br>General<br>
<br>General<br>
<br>Alcaligenes eutrophus (sometimes referred as Ralstonia metallidurans) is a gram negative bacillus with an optimum-growth temperature of 30oC [1]. It is a non-spore forming, obligate aerobic, and facultatively chemolithoautotrohpic bacterium that can thrive in environments containing mM concentrations of some toxic heavy metals such as Zinc, Cadmium, Cobalt, Lead, Mercury, Nickle, and Chromium [2]. In the presence of nitrate, A. eutrhopus can grow anaerobically. It naturally synthesizes polyhydroxybutyrate (PHB), a specific type of polyhydroxyalkanoates (PHA) that is used in the manufacture of biodegradable plastic.<br>
<br>Alcaligenes eutrophus (sometimes referred as Ralstonia metallidurans) is a gram negative bacillus with an optimum-growth temperature of 30oC [1]. It is a non-spore forming, obligate aerobic, and facultatively chemolithoautotrohpic bacterium that can thrive in environments containing mM concentrations of some toxic heavy metals such as Zinc, Cadmium, Cobalt, Lead, Mercury, Nickle, and Chromium [2]. In the presence of nitrate, A. eutrhopus can grow anaerobically. It naturally synthesizes polyhydroxybutyrate (PHB), a specific type of polyhydroxyalkanoates (PHA) that is used in the manufacture of biodegradable plastic.<br>
<br>The Enzymes: phbC-phbA-phbB<br>
<br>There are three regulatory enzymes involved in the bioproduction of PHB in Alcaligenes eutrophus: 3-ketothiolase, acetoacetyl-CoA reductase, and PHA syntase, encoded by by genes phbA, phbB, and phbC respectively. The molecular genetics and mapping of these enzymes were done in E. coli using the A. eutrophus strains of H16, 11599, 1159981, PHB 2, PHB3, PHB19.
In 1989, Sinskey and Peoples identified the location of phbA and phbB genes on plasmid pAeT29 of E. coli and that their expressions were under the control of Alcaligenes eutrophus promoter [1]. Later in the same year, the two researchers mapped the location phbC— phbC gene is located upstream from phbA-phbB. Additionally, they also observed a reduced activities in both thiolase and reeducate. Their results suggest that, in PHB2 and PHB3 strains, all three genes are expressed from the same promoter located upstream from phbC [1]<br>
<br>Moreover, Sinskey and Peoples also propose that Alcaligenes eutrophus has at least two P-ketothiolase and acetoace- tyl-CoA reductase enzymes. Thiolase  and reductase enzymes, when interact with either enoyl-CoA hydratase or epimerase or both,  can lead to the formation of D(-)-3-hydroxybutyryl-CoA. In E.coli the expression of phbC alone results in diminished amount of PHB synthesis and insignificant rate of PHB polymerase activity. The absence of both phbA and phB genes of A. eutrophus leads to no synthesis of D(-)-3-hydroxybutyryl-CoA. Only when the three A. eutrophus genes, phbC-phbA-phbB, are present in E. coli > 50% of PHB production was observed. They also figured that PHB production is inhibited by the presence of nitrogen.  Moreover, they propose that the interaction of thiolase and/ or reducatse with the polymerase is necessary for the polymerase to function.<br>


==Section 1==
==Section 1==

Revision as of 03:46, 26 April 2011

Introduction


By [Angel Mogie]

General

Alcaligenes eutrophus (sometimes referred as Ralstonia metallidurans) is a gram negative bacillus with an optimum-growth temperature of 30oC [1]. It is a non-spore forming, obligate aerobic, and facultatively chemolithoautotrohpic bacterium that can thrive in environments containing mM concentrations of some toxic heavy metals such as Zinc, Cadmium, Cobalt, Lead, Mercury, Nickle, and Chromium [2]. In the presence of nitrate, A. eutrhopus can grow anaerobically. It naturally synthesizes polyhydroxybutyrate (PHB), a specific type of polyhydroxyalkanoates (PHA) that is used in the manufacture of biodegradable plastic.


The Enzymes: phbC-phbA-phbB


There are three regulatory enzymes involved in the bioproduction of PHB in Alcaligenes eutrophus: 3-ketothiolase, acetoacetyl-CoA reductase, and PHA syntase, encoded by by genes phbA, phbB, and phbC respectively. The molecular genetics and mapping of these enzymes were done in E. coli using the A. eutrophus strains of H16, 11599, 1159981, PHB 2, PHB3, PHB19. In 1989, Sinskey and Peoples identified the location of phbA and phbB genes on plasmid pAeT29 of E. coli and that their expressions were under the control of Alcaligenes eutrophus promoter [1]. Later in the same year, the two researchers mapped the location phbC— phbC gene is located upstream from phbA-phbB. Additionally, they also observed a reduced activities in both thiolase and reeducate. Their results suggest that, in PHB2 and PHB3 strains, all three genes are expressed from the same promoter located upstream from phbC [1]


Moreover, Sinskey and Peoples also propose that Alcaligenes eutrophus has at least two P-ketothiolase and acetoace- tyl-CoA reductase enzymes. Thiolase and reductase enzymes, when interact with either enoyl-CoA hydratase or epimerase or both, can lead to the formation of D(-)-3-hydroxybutyryl-CoA. In E.coli the expression of phbC alone results in diminished amount of PHB synthesis and insignificant rate of PHB polymerase activity. The absence of both phbA and phB genes of A. eutrophus leads to no synthesis of D(-)-3-hydroxybutyryl-CoA. Only when the three A. eutrophus genes, phbC-phbA-phbB, are present in E. coli > 50% of PHB production was observed. They also figured that PHB production is inhibited by the presence of nitrogen. Moreover, they propose that the interaction of thiolase and/ or reducatse with the polymerase is necessary for the polymerase to function.

Section 1


Include some current research, with at least one figure showing data.

Section 2


Include some current research, with at least one figure showing data.

Section 3


Include some current research, with at least one figure showing data.

Conclusion


Overall text length at least 3,000 words, with at least 3 figures.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Joan Slonczewski for BIOL 238 Microbiology, 2011, Kenyon College.