新微生物基因系统剖析生物质降解过程

A research team at the DOE Great Lakes Bioenergy Research Center (GLBRC) has developed a powerful new tool that promises to unlock the secrets of biomass（生物量） degradation¹（降级，退化） , a critical step in the development of cost-effective cellulosic（有纤维质的） biofuels（生物燃料） . The details of this method were published online on June 11 in the journal Applied² and Environmental Microbiology. Fulfilling the promise of cellulosic biofuels requires developing efficient strategies to extract sugar molecules⁴ in biomass polymers（聚合物，高分子） like cellulose. Microorganisms such as bacteria and fungi⁵ are capable of converting biomass to simple sugars, but historically have been difficult to study using genetic⁷ approaches.

A breakthrough by a team of University of Wisconsin-Madison researchers at the GLBRC has made it possible to perform genetic analysis on Cellvibrio japonicus, a promising⁸ bacterium⁹ that has long been known to convert biomass to sugars. Using a technique called vector（矢量） integration¹⁰, the team has developed a method to generate a mutation¹¹ in any gene⁶ within the organism.

As a test of the technique, the team constructed a mutation that inactivated¹³ a key component¹⁴ of a protein complex called a Type II Secretion¹⁵ System, and the disruption of this system prevented the bacterium from efficiently¹⁶ converting biomass into sugars. This proves for the first time that Cellvibrio uses the Type II Secretion System to secrete¹⁷ key enzymes¹⁸ for breakdown¹⁹ of biomass polymerase（聚合酶） , thus providing key insight into how this bacterium obtains sugars from biomass.

"Realizing the promise of cellulosic biofuels requires identifying more efficient methods of releasing sugars from biomass", says GLBRC associate scientist David Keating, who led the team. "This new genetic method will allow us to understand how bacteria carry out this conversion²⁰, which should provide new avenues for improving the industrial process."

Plant cell wall deconstruction is a very complex process that requires a large number of enzymes, many with overlapping²¹ specificities, says Professor and Eminent²² Scholar in Bioenergy Harry²³ Gilbert, of the University of Georgia's Complex Carbohydrate²⁴ Research Center.

"As genetic systems for many bacteria that orchestrate（安排，协调） this process have not been developed, the use of null mutations (inactivating specific genes²⁵) to explore the functional²⁶ significance of specific enzymes has not been possible," says Gilbert. "Keating's group has provided the ability to do that — inactivate¹² specific genes in Cellvibrio japonicus — which displays an extensive plant cell wall degrading apparatus²⁷（装置，设备） . This enables you to ask critical biological questions about how the system is regulated and how the enzymes work together to degrade this hugely complex molecule³. This is a substantial and important development in the field."