RESUMEN
Capillary assemblies and microfluidic devices used for bacterial chemotaxis assays have certain inherent limitations. This opens opportunities for innovation in the area. The present study describes an innovative economical device called chemotaxis plate and also a method to use this device for chemotaxis assay. Two type cultures, Pseudomonas putida MCC 2989 and Bacillus subtilis MCC 2049, chemotactic to L-aspartate, were used to validate the new device and establish the protocol for assay. 100 to 1000 fold higher number of cells were recovered in presence of chemoattractant as compared to control (p < 0.05). This novel assay technique showed 100% sensitivity and 99.21% specificity for chemotaxis assay of Pseudomonas putida MCC 2989 towards 3 mM L-aspartate over 50 min assay time. The device was also used to isolate bacteria chemotactic to caffeine directly from environmental samples. Very high chemotaxis response indices were reported for the first-time using chemotaxis plate.
RESUMEN
The Antarctic continent hosts exceptional niches, making it an ideal environment for studying polyextremophilic microorganisms. These organisms are uniquely shaped by the geographic niches and variations in soil types. Here we present, a culture-independent approach using DNA metabarcoding to assess the bacterial communities associated with accumulated snow and exposed sediments across different Antarctic islands situated in the Larsemann Hills, Antarctica. The exposed sediments (ES) were found to be more diverse than the accumulated snow (AS) sediments as represented by the alpha diversity metrics. Out of the total 303 amplicon sequence variants (ASVs) found at the genus level, 93 were unique to accumulated snow sediments and 97 were unique to exposed sediments. The bacterial community composition in accumulated snow was dominated by the phylum Actinobacteriota (24.7%). However, Pseudonocardia (11.9%), Crossiella (11%), and Rhodanobacter (9.1%) were the predominant genera. In contrast, in the exposed sediments, Bacteroidota (24.6%) was the most prevalent phylum, with Crossiella (17.1%), Rhodanobacter (11.1%), and Blastocatella (10%) as the most abundant genera. Metagenomic imputations revealed the abundance of gene families responsible for carbon metabolism, coping with environmental stresses through DNA repair mechanisms, and carbon fixation.