Bacteria made to mimic cells, form communities

Bacteria made to mimic cells, form communities

Rice University scientists have found a way to engineer a new kind of cell differentiation in bacteria, inspired by a naturally occurring process in stem cells.

They have created a genetic circuit able to produce genetically distinguished cells of Escherichia coli as the bacterium divides. By controlling this process, it is possible to create diverse communities of microbes that exhibit complex, non-native behaviors.

Rice synthetic biologist Matthew Bennett and Sara Molinari, a former student in the university's Systems, Synthetic and Physical Biology Ph.D. program, led the project to show how manipulating the genetic code of plasmids -- free-floating pieces of circular DNA in cells -- can be used to obtain stem cell-like differentiation in bacteria.

"Stem cells have the remarkable ability to divide asymmetrically," Bennett said. "Upon division, the original stem cell stays the same, but the new daughter cell has a completely new phenotype. That's asymmetric cell division, and multicellular organisms use it to help control their cellular makeup.

"As a synthetic biologist, I think a lot about creating and controlling differentiated cell types within a multicellular population," he said. "Here, we've taken what we know about stem cells and engineered the means to do it in bacteria."

The researchers reported the development, which they call asymmetric plasmid partitioning (APP), in Nature Chemical Biology.

Molinari first discovered how to force plasmids in E. coli to aggregate in a single cluster so they do not distribute homogeneously during cell division, but rather are inherited by only one of the two daughter cells. The plasmid-laden daughter cell remains identical to the progenitor cell, while its sibling becomes genetically distinct as it loses the genetic information present on the plasmids.

She then expanded the synthetic circuit to induce the simultaneous asymmetric partitioning of two plasmid species in a single cell, resulting in four genetically distinct E. coli. Some of the cells have motility programmed in; they can literally go their own way and help form patterns in the resulting colony.

"When we started, we were thinking about creating materials that have to be able to sense and adapt to an environment," said Molinari, who recently earned her doctorate at Rice. "We thought if we could mimic this feature of higher-order tissues, we would increase the robustness of our colonies and their ability to perform tasks. The challenge was to engineer a population of bacteria that becomes something else whenever it's needed."

Molinari and her colleagues hit the jackpot on their first try with E. coli. "There was no canonical way to engineer asymmetrical cell division," she said. "It was a crazy idea, and it magically worked the first time.

"But there was something we couldn't completely figure out about the system," Molinari said. "It took two years to find out I made a cloning mistake when I got this protein and put it in my plasmid. I had randomly added 17 amino acids at the beginning of the protein, and that made the whole system work."

With that knowledge, she proceeded to improve upon the hydrophobic proteins that cluster in cells while they bind to target plasmids, holding them in place.

Bennett noted natural processes either load enough plasmids into a cell to ensure some land in each daughter cell or actively pull plasmids into each of the new cells to ensure they remain identical. "We have shown we can outcompete those processes," he said.

APP could turn simple organisms into complicated systems that enhance understanding of multicellular life. "We're pretty good at designing bacteria," Bennett said. "We've been doing that for years now. I think the field has evolved to the point where we can do amazing things with bacteria and people are asking what else we can do."

The new discovery, he said, provides a path forward.

"There are three main hallmarks to multicellular life," he said. "One is differentiation through asymmetric cell division. Another is intercellular communication, which synthetic biologists have been engineering for years. And the third is cell adhesion, so cells stay where they're supposed to and stick to each other. If we can control all those things together, we can talk about engineering interesting multicellular lifeforms.

"It starts to feel a bit like science fiction, for sure," he said.

---

Story Source:

Materials provided by Rice University. Original written by Mike Williams. Note: Content may be edited for style and length.

Teens are using a highly potent form of marijuana

Cannabis sativa plant

Nearly one in four Arizona teens have used a highly potent form of marijuana known as marijuana concentrate, according to a new study by Arizona State University researchers.

Among nearly 50,000 eighth, 10th, and 12th graders from the 2018 Arizona Youth Survey, a biennial survey of Arizona secondary school students, one-third (33%) had tried some form of marijuana, and nearly a quarter (24%) had tried marijuana concentrate.

Marijuana concentrates have about three times more THC, the constituent of marijuana that causes the "high," than a traditional marijuana flower. This is concerning because higher doses of THC have been linked to increased risk of marijuana addiction, cognitive impairment and psychosis, said the study's lead researcher, Madeline Meier, an ASU assistant professor of psychology.

The research team also found that teens who used concentrates had more risk factors for addiction. The researchers compared teens who had used marijuana concentrates with teens who had used some form of marijuana but not marijuana concentrates and teens who had never used any form of marijuana on known risk factors for addiction, such as lower perceived risk of harm of marijuana, peer substance use, parental substance use, academic failure and greater perceived availability of drugs in the community. They found that teens who had used marijuana concentrates were worse off on every addiction risk factor.

"This is important because it shows that teens who have a diverse array of risk factors for developing marijuana addiction may be further amplifying their risk for addiction by using high-THC marijuana concentrates," explained study co-author, Dustin Pardini, an associate professor in ASU's School of Criminology & Criminal Justice.

The study "Cannabis Concentrate Use in Adolescents," is published in the early online edition (Aug. 26, 2019) of Pediatrics.

The team -- which includes ASU researchers Meagan Docherty, School of Criminology & Criminal Justice; Scott Leischow, College of Health Solutions; and Kevin Grimm, Department of Psychology -- also found that teens who had used concentrates had much higher rates of e-cigarette use. One explanation for this might be that teens are using e-cigarettes to vape marijuana concentrate, according to Meier. Earlier studies, including those by Meier, have shown that youth put marijuana in e-cigarettes to conceal their marijuana use.

"Vaping marijuana can be passed off as nicotine vaping," Meier explained.

This finding reinforces the recent decision by the Food and Drug Administration to impose new restrictions on e-cigarettes and their constituents as a means of reducing marijuana use, according to the researchers.

Marijuana concentrates don't look like the traditional marijuana flower. Concentrates can look like wax, oil, or a brittle substance that shatters easily.

"What concerns me most is that parents might have no idea that their child is using marijuana, especially if their child is using marijuana concentrate," said Meier. "Marijuana is not harmless, particularly for adolescents."

Meier's earlier research suggests that frequent marijuana use from adolescence through adulthood is associated with IQ decline. Pardini's prior research has linked regular marijuana use during adolescence with the emergence of persistent subclinical psychotic symptoms.

The researchers' next steps are to ascertain if concentrate users do in fact exhibit higher rates of addiction, cognitive impairment and psychosis.

The Arizona Youth Survey is administered by the Arizona Criminal Justice Commission (ACJC) through funds appropriated by the Arizona Legislature.

Bacteria made to mimic cells, form communities

Bacteria made to mimic cells

Rice University scientists have found a way to engineer a new kind of cell differentiation in bacteria, inspired by a naturally occurring process in stem cells.

They have created a genetic circuit able to produce genetically distinguished cells of Escherichia coli as the bacterium divides. By controlling this process, it is possible to create diverse communities of microbes that exhibit complex, non-native behaviors.

Rice synthetic biologist Matthew Bennett and Sara Molinari, a former student in the university's Systems, Synthetic and Physical Biology Ph.D. program, led the project to show how manipulating the genetic code of plasmids -- free-floating pieces of circular DNA in cells -- can be used to obtain stem cell-like differentiation in bacteria.

"Stem cells have the remarkable ability to divide asymmetrically," Bennett said. "Upon division, the original stem cell stays the same, but the new daughter cell has a completely new phenotype. That's asymmetric cell division, and multicellular organisms use it to help control their cellular makeup.

"As a synthetic biologist, I think a lot about creating and controlling differentiated cell types within a multicellular population," he said. "Here, we've taken what we know about stem cells and engineered the means to do it in bacteria."

The researchers reported the development, which they call asymmetric plasmid partitioning (APP), in Nature Chemical Biology.

Molinari first discovered how to force plasmids in E. coli to aggregate in a single cluster so they do not distribute homogeneously during cell division, but rather are inherited by only one of the two daughter cells. The plasmid-laden daughter cell remains identical to the progenitor cell, while its sibling becomes genetically distinct as it loses the genetic information present on the plasmids.

She then expanded the synthetic circuit to induce the simultaneous asymmetric partitioning of two plasmid species in a single cell, resulting in four genetically distinct E. coli. Some of the cells have motility programmed in; they can literally go their own way and help form patterns in the resulting colony.

"When we started, we were thinking about creating materials that have to be able to sense and adapt to an environment," said Molinari, who recently earned her doctorate at Rice. "We thought if we could mimic this feature of higher-order tissues, we would increase the robustness of our colonies and their ability to perform tasks. The challenge was to engineer a population of bacteria that becomes something else whenever it's needed."

Molinari and her colleagues hit the jackpot on their first try with E. coli. "There was no canonical way to engineer asymmetrical cell division," she said. "It was a crazy idea, and it magically worked the first time.

"But there was something we couldn't completely figure out about the system," Molinari said. "It took two years to find out I made a cloning mistake when I got this protein and put it in my plasmid. I had randomly added 17 amino acids at the beginning of the protein, and that made the whole system work."

With that knowledge, she proceeded to improve upon the hydrophobic proteins that cluster in cells while they bind to target plasmids, holding them in place.

Bennett noted natural processes either load enough plasmids into a cell to ensure some land in each daughter cell or actively pull plasmids into each of the new cells to ensure they remain identical. "We have shown we can outcompete those processes," he said.

APP could turn simple organisms into complicated systems that enhance understanding of multicellular life. "We're pretty good at designing bacteria," Bennett said. "We've been doing that for years now. I think the field has evolved to the point where we can do amazing things with bacteria and people are asking what else we can do."

The new discovery, he said, provides a path forward.

"There are three main hallmarks to multicellular life," he said. "One is differentiation through asymmetric cell division. Another is intercellular communication, which synthetic biologists have been engineering for years. And the third is cell adhesion, so cells stay where they're supposed to and stick to each other. If we can control all those things together, we can talk about engineering interesting multicellular lifeforms.

"It starts to feel a bit like science fiction, for sure," he said.

---

Story Source:

Materials provided by Rice University. Original written by Mike Williams. Note: Content may be edited for style and length.

Bacteria made to mimic cells, form communities

Bacteria

Rice University scientists have found a way to engineer a new kind of cell differentiation in bacteria, inspired by a naturally occurring process in stem cells.

They have created a genetic circuit able to produce genetically distinguished cells of Escherichia coli as the bacterium divides. By controlling this process, it is possible to create diverse communities of microbes that exhibit complex, non-native behaviors.

Rice synthetic biologist Matthew Bennett and Sara Molinari, a former student in the university's Systems, Synthetic and Physical Biology Ph.D. program, led the project to show how manipulating the genetic code of plasmids -- free-floating pieces of circular DNA in cells -- can be used to obtain stem cell-like differentiation in bacteria.

"Stem cells have the remarkable ability to divide asymmetrically," Bennett said. "Upon division, the original stem cell stays the same, but the new daughter cell has a completely new phenotype. That's asymmetric cell division, and multicellular organisms use it to help control their cellular makeup.

"As a synthetic biologist, I think a lot about creating and controlling differentiated cell types within a multicellular population," he said. "Here, we've taken what we know about stem cells and engineered the means to do it in bacteria."

The researchers reported the development, which they call asymmetric plasmid partitioning (APP), in Nature Chemical Biology.

Molinari first discovered how to force plasmids in E. coli to aggregate in a single cluster so they do not distribute homogeneously during cell division, but rather are inherited by only one of the two daughter cells. The plasmid-laden daughter cell remains identical to the progenitor cell, while its sibling becomes genetically distinct as it loses the genetic information present on the plasmids.

She then expanded the synthetic circuit to induce the simultaneous asymmetric partitioning of two plasmid species in a single cell, resulting in four genetically distinct E. coli. Some of the cells have motility programmed in; they can literally go their own way and help form patterns in the resulting colony.

"When we started, we were thinking about creating materials that have to be able to sense and adapt to an environment," said Molinari, who recently earned her doctorate at Rice. "We thought if we could mimic this feature of higher-order tissues, we would increase the robustness of our colonies and their ability to perform tasks. The challenge was to engineer a population of bacteria that becomes something else whenever it's needed."

Molinari and her colleagues hit the jackpot on their first try with E. coli. "There was no canonical way to engineer asymmetrical cell division," she said. "It was a crazy idea, and it magically worked the first time.

"But there was something we couldn't completely figure out about the system," Molinari said. "It took two years to find out I made a cloning mistake when I got this protein and put it in my plasmid. I had randomly added 17 amino acids at the beginning of the protein, and that made the whole system work."

With that knowledge, she proceeded to improve upon the hydrophobic proteins that cluster in cells while they bind to target plasmids, holding them in place.

Bennett noted natural processes either load enough plasmids into a cell to ensure some land in each daughter cell or actively pull plasmids into each of the new cells to ensure they remain identical. "We have shown we can outcompete those processes," he said.

APP could turn simple organisms into complicated systems that enhance understanding of multicellular life. "We're pretty good at designing bacteria," Bennett said. "We've been doing that for years now. I think the field has evolved to the point where we can do amazing things with bacteria and people are asking what else we can do."

The new discovery, he said, provides a path forward.

"There are three main hallmarks to multicellular life," he said. "One is differentiation through asymmetric cell division. Another is intercellular communication, which synthetic biologists have been engineering for years. And the third is cell adhesion, so cells stay where they're supposed to and stick to each other. If we can control all those things together, we can talk about engineering interesting multicellular lifeforms.

"It starts to feel a bit like science fiction, for sure," he said.

---

Story Source:

Materials provided by Rice University. Original written by Mike Williams. Note: Content may be edited for style and length.