Efficient strategies were developed
for the synthesis of 6-deoxy-d-manno-heptopyranose
and its β-(1 →
3)-linked oligomers as fragments of the common and major capsular
polysaccharide, type I O-PS, of Burkholderia pseudomallei and Burkholderia mallei. The unusual
heptose was synthesized from mannose, highlighted by the facile Wittig
reaction and anti-Markovnikov hydroboration of the resultant olefin.
The difficult β-mannosidic linkage in the oligosaccharides was
achieved in high stereoselectivity by H-bond-mediated aglycone delivery.
All of the oligosaccharides were conjugated with the carrier protein
CRM197. Preliminary immunological evaluations of the resultant
glycoconjugates in mice verified their efficacy to elicit high titers
of immunoglobulin G antibodies and robust T-cell-dependent immune
responses. It was also found that the trisaccharide conjugates provoked
the strongest immune responses, worthy of further in-depth study for
vaccine development.
Cyanobacteria are ever-present, mainly flourishing in aquatic environments and surviving virtually in other habitats. The microbiota of indoor dust on the pre-filter of heating, ventilation, and air-conditioning (HVAC) systems, which reflect indoor microbial contamination and affect human health, has attracted attention. Contemporary studies on cyanobacteria deposited on the pre-filter of HVAC remain scant. By the culture-independent approach of qPCR and high throughput sequencing technologies, our results documented that the cyanobacterial concentrations were highest in autumn, occurred recurrently, and were about 2.60 and 10.57-fold higher than those in winter and summer. We proposed that aquatic and terrestrial cyanobacteria contributed to the pre-filter of HVAC by airborne transportation produced by wave breaks, bubble bursts, and soil surface by wind force, owing to the evidence that cyanobacteria were commonly detected in airborne particulate matters. The cyanobacteria community structure was characterized in Shanghai, where Chroococcidiopsaceae, norank_cyanobacteriales, Nostocaceae, Paraspirulinaceae, and others dominated the dust on the pre-filter of HVAC. Some detected genera, including Nodularia sp., Pseudanabaena sp., and Leptolyngbya sp., potentially produced cyanobacterial toxins, which need further studying to determine their potential threat to human health. The present work shed new insight into cyanobacteria distribution in the specific environment besides aquatic habitats.
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