Novel Quorum Sensing Activity in East Antarctic Soil Bacteria

Abstract

Antarctica, being the coldest, driest and windiest continent on Earth, represents the most extreme environment a living organism can thrive in. Under constant exposure to harsh environmental threats, terrestrial Antarctica remains home to a great diversity of microorganisms, indicating that the soil bacteria must have adapted a range of survival strategies that require cell-to-cell communication. Survival strategies include secondary metabolite production, biofilm formation, bioluminescence, symbiosis, conjugation, sporulation and motility, all of which are often regulated by quorum sensing (QS), a type of bacterial communication. Up to now, such mechanisms have not been explored in terrestrial Antarctica. Here, for the first time, LuxI/LuxR-based quorum sensing (QS) activity was delineated in soil bacterial isolates recovered from Adams Flat, in the Vestfold Hills region of East Antarctica. Interestingly, we identified the production of potential homoserine lactones (HSLs) ranging from medium to long chain length in 19 bacterial species using three biosensors, namely Agrobacterium tumefaciens NTL4, Chromobacterium violaceum CV026 and Escherichia coli MT102, in conjunction with thin layer chromatography (TLC). The majority of detectable HSLs were from gram-positive microorganisms not previously known to produce HSLs. This discovery further expands our understand of the microbial community capable of this type of communication, as well as providing insights into physiological adaptations of microorganisms that allow them to survive in the harsh Antarctic environment.IMPORTANCEQuorum sensing, a type of bacterial communication, is widely known to regulate many processes including those that confer survival advantage. However, little is known about communication by bacteria thriving within Antarctic soils. Employing a combination of bacteria biosensors, analytical techniques, and genome mining, we found a variety of Antarctic soil bacteria speaking a common language, via the LuxI/LuxR-based quorum sensing, thus potentially supporting survival in a mixed microbial community. This is the first report of quorum sensing activity in Antarctic soils and has provided a platform for studying physiological adaptations of microorganisms that allow them to not just survive but thrive in the harsh Antarctic environment.

Dominant plant species play an important role in regulating bacterial antagonism in terrestrial Antarctica

“…Antarctica is the coldest, driest, and windiest continent and is considered one of the harshest environments for biodiversity (Chown et al, 2015;Wong et al, 2019), yet it harbors surprisingly complex communities with high bacterial diversity (Smith et al, 2010). The diversity and composition of soil microbiomes in Antarctica have been documented in several studies (O'Brien et al, 2004;Wong et al, 2011;Bottos et al, 2014;Peixoto et al, 2016;Malard and Pearce, 2018;Malcheva et al, 2020;Zhang et al, 2020) which have shown that bacterial communities across Antarctic soils vary significantly not only with climate, geography and local biological influences, but also with plant type (Griffiths et al, 2011;Xiong et al, 2012;Yun et al, 2014).…”