NEWS - Scientists are looking for alternative plastic products that are more sustainable, more biodegradable and far less toxic to the environment. Researchers at Washington University in St. Louis are using Rhodopseudomonas palustris, Rhodomicrobium vannielii and Rhodomicrobium udaipurense to replace petroleum-based plastics.
The bacteria, with a little encouragement, are expected to become microscopic factories for bioplastics. The ability to produce polyhydroxyalkanoates (PHAs), natural polymers that can be purified to make plastics. Eventually, genetic engineering could coax the bacteria to increase their PHA production.
"There is a huge global demand for bioplastics. They can be produced without adding CO2 to the atmosphere and are completely biodegradable. Our two studies show the importance of taking a multi-pronged approach to finding new ways to produce these valuable materials," said Arpita Bose of Wash. University.
Purple bacteria are a special group of aquatic microbes that have the ability to adapt and create useful compounds from simple ingredients. They can convert carbon dioxide into food using energy from the sun. Another pigment to capture sunlight instead of green chlorophyll.
The researchers assessed the photosynthetic purple non-sulfur bacteria R. vannielii and R. udaipurense for their ability to accumulate PHA across photo-heterotrophic, photo-hydrogenotrophic, photo-ferrotrophic and photo-electrotrophic growth conditions with ammonium chloride (NH4Cl) or dinitrogen gas (N2) as the nitrogen source.
They naturally produce PHA and other bioplastic building blocks to store extra carbon. Under the right conditions, they can continue producing the polymers indefinitely. There is a tremendous appetite for producing polymers, especially when energized with small amounts of electricity and fed with nitrogen.
“We have to look at bacteria that we’ve never seen before. We haven’t been able to realize their potential. These are unique bacteria that look very different from other purple bacteria,” said Eric Conners of Wash. University.
Rhodomicrobium bacteria have unusual properties that make them interesting contenders as natural bioplastic factories. While some species live in culture as individual cells, this particular genus forms interconnected networks that seem particularly well-suited to producing PHAs.
Other types of bacteria can also produce bioplastic polymers, with the help of genetic engineering to produce impressive levels of PHA from Rhodopseudomonas palustris TIE-1, a well-studied species that is typically reluctant to produce polymers.
“TIE-1 is a great organism to study, but historically it’s not the best at producing PHAs,” said Tahina Ranaivoarisoa of Wash. University.
Several genetic changes have helped boost PHA production, but one approach has been particularly successful. The researchers saw impressive results when they inserted a gene that enhances the natural enzyme RuBisCO, a catalyst that helps plants and bacteria capture carbon from the air and water.
Inserting a copy of the RuBisCO gene into the TIE-1 genome was a more effective strategy than deleting competing pathways to boost PHA production in TIE-1. The successful use of the phage integration system opens up a wealth of opportunities for synthetic biology in TIE-1.
The normally sluggish bacteria became relatively large PHA powerhouses after being given the super-potent enzyme. The researchers are optimistic that a similar approach could be applied to other bacteria that might be able to produce bioplastics in greater quantities.
Original research
Ranaivoarisoa TO, Bai W, Karthikeyan R, Steele H, Silberman M, Olabode J, Conners E, Gallagher B, Bose A. 0. Overexpression of RuBisCO form I and II genes in Rhodopseudomonas palustris TIE-1 augments polyhydroxyalkanoate production heterotrophically and autotrophically. Applied and Industrial Microbiology 0:e01438-24 (2024). DOI:10.1128/aem.01438-24
Eric M. Conners, Karthikeyan Rengasamy, Tahina Ranaivoarisoa, Arpita Bose. The phototrophic purple non-sulfur bacteria Rhodomicrobium spp. are novel chassis for bioplastic production. Microbial Biotechnology, Volume17, Issue 8, August 2024, e14552 DOI:10.1111/1751-7915.14552
The bacteria, with a little encouragement, are expected to become microscopic factories for bioplastics. The ability to produce polyhydroxyalkanoates (PHAs), natural polymers that can be purified to make plastics. Eventually, genetic engineering could coax the bacteria to increase their PHA production.
"There is a huge global demand for bioplastics. They can be produced without adding CO2 to the atmosphere and are completely biodegradable. Our two studies show the importance of taking a multi-pronged approach to finding new ways to produce these valuable materials," said Arpita Bose of Wash. University.
Purple bacteria are a special group of aquatic microbes that have the ability to adapt and create useful compounds from simple ingredients. They can convert carbon dioxide into food using energy from the sun. Another pigment to capture sunlight instead of green chlorophyll.
The researchers assessed the photosynthetic purple non-sulfur bacteria R. vannielii and R. udaipurense for their ability to accumulate PHA across photo-heterotrophic, photo-hydrogenotrophic, photo-ferrotrophic and photo-electrotrophic growth conditions with ammonium chloride (NH4Cl) or dinitrogen gas (N2) as the nitrogen source.
They naturally produce PHA and other bioplastic building blocks to store extra carbon. Under the right conditions, they can continue producing the polymers indefinitely. There is a tremendous appetite for producing polymers, especially when energized with small amounts of electricity and fed with nitrogen.
“We have to look at bacteria that we’ve never seen before. We haven’t been able to realize their potential. These are unique bacteria that look very different from other purple bacteria,” said Eric Conners of Wash. University.
Rhodomicrobium bacteria have unusual properties that make them interesting contenders as natural bioplastic factories. While some species live in culture as individual cells, this particular genus forms interconnected networks that seem particularly well-suited to producing PHAs.
Other types of bacteria can also produce bioplastic polymers, with the help of genetic engineering to produce impressive levels of PHA from Rhodopseudomonas palustris TIE-1, a well-studied species that is typically reluctant to produce polymers.
“TIE-1 is a great organism to study, but historically it’s not the best at producing PHAs,” said Tahina Ranaivoarisoa of Wash. University.
Several genetic changes have helped boost PHA production, but one approach has been particularly successful. The researchers saw impressive results when they inserted a gene that enhances the natural enzyme RuBisCO, a catalyst that helps plants and bacteria capture carbon from the air and water.
Inserting a copy of the RuBisCO gene into the TIE-1 genome was a more effective strategy than deleting competing pathways to boost PHA production in TIE-1. The successful use of the phage integration system opens up a wealth of opportunities for synthetic biology in TIE-1.
The normally sluggish bacteria became relatively large PHA powerhouses after being given the super-potent enzyme. The researchers are optimistic that a similar approach could be applied to other bacteria that might be able to produce bioplastics in greater quantities.
Original research
Ranaivoarisoa TO, Bai W, Karthikeyan R, Steele H, Silberman M, Olabode J, Conners E, Gallagher B, Bose A. 0. Overexpression of RuBisCO form I and II genes in Rhodopseudomonas palustris TIE-1 augments polyhydroxyalkanoate production heterotrophically and autotrophically. Applied and Industrial Microbiology 0:e01438-24 (2024). DOI:10.1128/aem.01438-24
Eric M. Conners, Karthikeyan Rengasamy, Tahina Ranaivoarisoa, Arpita Bose. The phototrophic purple non-sulfur bacteria Rhodomicrobium spp. are novel chassis for bioplastic production. Microbial Biotechnology, Volume17, Issue 8, August 2024, e14552 DOI:10.1111/1751-7915.14552
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