A modified iChip for in situ cultivation of bacteria in arid environments

Antimicrobial resistance is an ever-increasing problem for human health, and with only a few novel antimicrobials discovered in recent decades, an extraordinary effort is needed to circumvent this crisis. A promising source of new microbial-derived antimicrobial compounds resides in the large fraction of microbes that are not readily cultured by standard cultivation. It has previously been shown that nests of the social spider Stegodyphus dumicola contain a diverse bacterial community, where only a small fraction of the microbes could be recovered by standard cultivation. To improve the recovery of the bacterial diversity cultured from nests, we modified the previously described isolation chip (iChip) to fit the natural arid environment of S. dumicola nests. Here we provide a comprehensive analysis of the modified iChip's performance. We found that the modified iChip improved the overall culturability, performed equally or better at recovering the bacterial diversity from individual nests, and improved the recovery of rare isolates compared to standard cultivation. Furthermore, we show that the modified iChip can be used in the field. In addition, we observed that the nests contain volatile organic compounds (VOCs) that could serve as substrate for the selective enrichment of rare and iChip-specific isolates. Our modified iChip can be applied for in situ cultivation in a broad range of arid habitats that can be exploited for future drug discovery.IMPORTANCEThe demand for novel antimicrobial compounds is an ever-increasing problem due to the rapid spread of antibiotic-resistant microbes. Therefore, exploring new habitats for microbial-derived antimicrobial compounds is crucial. The nest microbiome of Stegodyphus dumicola remains largely unexplored and could potentially serve as a new source of antimicrobial compounds. To access the nest's microbial diversity, we designed a modified iChip for in situ cultivation inside spider nests and tested its applications in both field and laboratory settings. Our study shows that the iChip's ability to recover in situ abundant genera was comparable or superior to standard cultivation, while the recovery of rare (low-abundant genera) was higher. We argue that these low-abundant and iChip-specific isolates are enriched from naturally occurring nest volatile organic compounds (VOCs) during iChip incubation.