Cultivation of gut microorganisms of the marine ascidian Halocynthia roretzi reveals their potential roles in the environmental adaptation of their host

It has long been known that abundant symbiotic bacteria exist in the tunic and gut of marine ascidians,and that these play crucial roles in host development,physiological metabolism,and environmental adaptation.However,the identity,roles and functions of these symbiotic bacteria are known for only a few strains.In this study,we isolated and cultivated 263 strains of microorganisms from the intestine of the marine ascidian Halocynthia roretzi through a combination of aerobic and anaerobic culture approaches.Most cultivated species,both aerobic and anaerobic,from ascidian stool samples belonged to the genus Bacillus based on 16S rDNA sequencing identification and phylogenetic assays.The distribution of cultured bacteria varied with seasonal changes in environmental conditions.To explore the functions of cultured bacteria,we screened out a strain of Serratia sp.whose extracts showed high antibacterial activity against aquatic pathogens.These findings revealed the potential roles of gut microorganisms in ascidian defense and environmental adaptation,thus providing insights into the interaction and co-evolution between gut bacteria and their hosts.

Biodegradation of waste refrigerator polyurethane by mealworms

Refrigerator insulation replacement results in discarding a large amount of waste refrigerator polyurethane(WRPU).Insect larvae like mealworms have been used to biodegrade pristine plastics.However,knowledge about mealworms degrading WRPU is scarce.This study presents an in-depth investigation of the degradation of WRPU by mealworms using the micro-morphology,composition,and functional groups of WRPU and the egested frass characteristics.It was found that the WRPU debris in frass was scoured,implying that WRPU was ingested and degraded by mealworms.The carbon content of WRPU-based frass was lower than that of WRPU,indicating that mealworms utilized WRPU as a carbon source.The urethane groups in WRPU were broken,and benzene rings’C=C and C–H bonds in the isocyanate disappeared after being ingested by mealworms.Thermal gravimetric-differential thermal gravimetry analysis showed that the weight loss temperature of WRPU-based frass was 300°C lower than that of WRPU,indicating that the thermal stability of WRPU deteriorated after being ingested.The carbon balance analysis confirmed that carbon in the ingested WRPU released as CO_(2) increased from 18.84%to 29.80%,suggesting that WRPU was partially mineralized.The carbon in the mealworm biomass ingesting WRPU decreased.The possible reason is that WRPU does not supply sufficient nutrients for mealworm growth,and the impurities and odor present in WRPU affect the appetite of the mealworms.The microbial community analysis indicated that WRPU exerts a considerable effect on the gut microorganism of mealworms.These findings confirm that mealworms degrade WRPU.