Ultrasound-mediated DNA transformation in thermophilic gram-positive anaerobes.
BACKGROUND
Thermophilic, Gram-positive, anaerobic bacteria (TGPAs) are generally recalcitrant to chemical and electrotransformation due to their special cell-wall structure and the low intrinsic permeability of plasma membranes.


RESULTS
Here we established for any Gram-positive or thermophiles an ultrasound-based sonoporation as a simple, rapid, and minimally invasive method to genetically transform TGPAs. We showed that by applying a 40 kHz ultrasound frequency over a 20-second exposure, Texas red-conjugated dextran was delivered with 27% efficiency into Thermoanaerobacter sp. X514, a TGPA that can utilize both pentose and hexose for ethanol production. Experiments that delivered plasmids showed that host-cell viability and plasmid DNA integrity were not compromised. Via sonoporation, shuttle vectors pHL015 harboring a jellyfish gfp gene and pIKM2 encoding a Clostridium thermocellum β-1,4-glucanase gene were delivered into X514 with an efficiency of 6x10(2) transformants/µg of methylated DNA. Delivery into X514 cells was confirmed via detecting the kanamycin-resistance gene for pIKM2, while confirmation of pHL015 was detected by visualization of fluorescence signals of secondary host-cells following a plasmid-rescue experiment. Furthermore, the foreign β-1,4-glucanase gene was functionally expressed in X514, converting the host into a prototypic thermophilic consolidated bioprocessing organism that is not only ethanologenic but cellulolytic.


CONCLUSIONS
In this study, we developed an ultrasound-based sonoporation method in TGPAs. This new DNA-delivery method could significantly improve the throughput in developing genetic systems for TGPAs, many of which are of industrial interest yet remain difficult to manipulate genetically.
Lin
Lu
L
Qingdao Institute of BioEnergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, China.
Song
Houhui
H
Ji
Yuetong
Y
He
Zhili
Z
Pu
Yunting
Y
Zhou
Jizhong
J
Xu
Jian
J
D001421:Bacteria, Anaerobic / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics*; D018014:Gene Transfer Techniques / Q000295:instrumentation; D006358:Hot Temperature; D010957:Plasmids / Q000235:genetics; D046968:Thermoanaerobacter / Q000235:genetics*; D014169:Transformation, Bacterial; D014465:Ultrasonics
D004269:DNA, Bacterial