Development of label-free electrochemical OMP-DNA probe biosensor as a highly sensitive system to detect of citrus huanglongbing

The fabrication of the first label-free electrochemical DNA probe biosensor for highly sensitive detection of Candidatus Liberibacter asiaticus (CLas), as the causal agent of citrus huanglongbing disease, is conducted here. An OMP probe was designed based on the hybridization with its target-specific sequence in the outer membrane protein (OMP) gene of CLas. The characterization of the steps of biosensor fabrication and hybridization process between the immobilized OMP-DNA probe and the target ssDNA oligonucleotides (OMP-complementary and three mismatches OMP or OMP-mutation) was monitored using cyclic voltammetry and electrochemical impedance spectroscopy based on increasing or decreasing in the electron transfer in [Fe (CN)6]3-/4- on the modified gold electrode surface. The biosensor sensitivity indicated that the peak currents were linear over ranges from 20 to 100 nM for OMP-complementary with the detection limit of 0.026 nM (S/N = 3). The absence of any cross-interference with other biological DNA sequences confirmed a high selectivity of fabricated biosensor. Likewise, it showed good specificity in discriminating the mutation oligonucleotides from complementary target DNAs. The functional performance of optimized biosensor was achieved via the hybridization of OMP-DNA probe with extracted DNA from citrus plant infected with CLas. Therefore, fabricated biosensor indicates promise for sensitivity and early detection of citrus huanglongbing disease.

Lipidomic diversity and proxy implications of archaea from cold seep sediments of the South China Sea

Cold seeps on the continental margins are characterized by intense microbial activities that consume a large portion of methane by anaerobic methanotrophic archaea (ANME) through anaerobic oxidation of methane (AOM). Although ANMEs are known to contain unique ether lipids that may have an important function in marine carbon cycling, their full lipidomic profiles and functional distribution in particular cold-seep settings are still poorly characterized. Here, we combined the 16S rRNA gene sequencing and lipidomic approaches to analyze archaeal communities and their lipids in cold seep sediments with distinct methane supplies from the South China Sea. The archaeal community was dominated by ANME-1 in the moderate seepage area with strong methane emission. Low seepage area presented higher archaeal diversity covering Lokiarchaeia, Bathyarchaeia, and Thermoplasmata. A total of 55 core lipids (CLs) and intact polar lipids (IPLs) of archaea were identified, which included glycerol dialkyl glycerol tetraethers (GDGTs), hydroxy-GDGTs (OH-GDGTs), archaeol (AR), hydroxyarchaeol (OH-AR), and dihydroxyarchaeol (2OH-AR). Diverse polar headgroups constituted the archaeal IPLs. High concentrations of dissolved inorganic carbon (DIC) with depleted δ13CDIC and high methane index (MI) values based on both CLs (MICL) and IPLs (MIIPL) indicate that ANMEs were active in the moderate seepage area. The ANME-2 and ANME-3 clades were characterized by enhanced glycosidic and phosphoric diether lipids production, indicating their potential role in coupling carbon and phosphurus cycling in cold seep ecosystems. ANME-1, though representing a smaller proportion of total archaea than ANME-2 and ANME-3 in the low seepage area, showed a positive correlation with MIIPL, indicating a different mechanism contributing to the IPL-GDGT pool. This also suggests that MIIPL could be a sensitive index to trace AOM activities performed by ANME-1. Overall, our study expands the understanding of the archaeal lipid composition in the cold seep and improves the application of MI using intact polar lipids that potentially link to extent ANME activities.

Point-of-Need DNA Testing for Detection of Foodborne Pathogenic Bacteria

Foodborne pathogenic bacteria present a crucial food safety issue. Conventional diagnostic methods are time-consuming and can be only performed on previously produced food. The advancing field of point-of-need diagnostic devices integrating molecular methods, biosensors, microfluidics, and nanomaterials offers new avenues for swift, low-cost detection of pathogens with high sensitivity and specificity. These analyses and screening of food items can be performed during all phases of production. This review presents major developments achieved in recent years in point-of-need diagnostics in land-based sector and sheds light on current challenges in achieving wider acceptance of portable devices in the food industry. Particular emphasis is placed on methods for testing nucleic acids, protocols for portable nucleic acid extraction and amplification, as well as on the means for low-cost detection and read-out signal amplification.