The alterations of oral, airway and intestine microbiota in chronic obstructive pulmonary disease: a systematic review and meta-analysis.

Background: Increasing evidence indicates the microbial ecology of chronic obstructive pulmonary disease (COPD) is intricately associated with the disease's status and severity, and distinct microbial ecological variations exist between COPD and healthy control (HC). This systematic review and meta-analysis aimed to summarize microbial diversity indices and taxa relative abundance of oral, airway, and intestine microbiota of different stages of COPD and HC to make comparisons. Methods: A comprehensive systematic literature search was conducted in PubMed, Embase, the Web of Science, and the Cochrane Library databases to identify relevant English articles on the oral, airway, and intestine microbiota in COPD published between 2003 and 8 May 2023. Information on microbial diversity indices and taxa relative abundance of oral, airway, and intestine microbiota was collected for comparison between different stages of COPD and HC. Results: A total of 20 studies were included in this review, involving a total of 337 HC participants, 511 COPD patients, and 154 AECOPD patients. We observed that no significant differences in alpha diversity between the participant groups, but beta diversity was significantly different in half of the included studies. Compared to HC, Prevotella, Streptococcus, Actinomyces, and Veillonella of oral microbiota in SCOPD were reduced at the genus level. Most studies supported that Haemophilus, Lactobacillus, and Pseudomonas were increased, but Veillonella, Prevotella, Actinomyces, Porphyromonas, and Atopobium were decreased at the genus level in the airway microbiota of SCOPD. However, the abundance of Haemophilus, Lactobacillus and Pseudomonas genera exhibited an increase, whereas Actinomyces and Porphyromonas showed a decrease in the airway microbiota of AECOPD compared to HC. And Lachnospira of intestine microbiota in SCOPD was reduced at the genus level. Conclusion: The majority of published research findings supported that COPD exhibited decreased alpha diversity compared to HC. However, our meta-analysis does not confirm it. In order to further investigate the characteristics and mechanisms of microbiome in the oral-airway- intestine axis of COPD patients, larger-scale and more rigorous studies are needed. Systematic review registration: PROSPERO (https://www.crd.york.ac.uk/prospero/), identifier CRD42023418726.

Supplementary sulfide during inoculation for improved sulfur autotrophic denitrification performance and adaptation to low temperature.

Elemental sulfur (S0) autotrophic denitrification (SAD) has been considered an advanced denitrification technology due to its low operating cost and small secondary pollution in wastewater treatment plants. However, the wide application of this technology is still challenged by its low denitrification rate, long start-up time, and poor low-temperature adaptation. This study employed supplementary sulfide to facilitate the conversion of S0 into polysulfide, a critical step in SAD. Batch experiments indicated that more polysulfide could be generated when S0 served as an electron donor and partnered with additional Na2S, leading to greatly increased nitrate removal than the controls. Particularly when the sulfide concentration was relatively high at 160 mg/L, a denitrification rate up to 11.3 mg-N/(L·d) was achieved, 3.8-fold of control group working with solely S0. Sulfide was further applied during inoculation of a packed bed reactor (PBR) with S0 particles and significantly benefit the development of biofilm. Although the feeding of sulfide was stopped after inoculation, the reactor was fast started up in just 2 days and delivered an average denitrification rate of 346.9 mg-N/(L·d), 1.4-fold of the control. In addition, benefit from the thick and well-developed biofilm, the reactor was able to restore its nitrate removal performance, when challenged by a low temperature (15 °C), to a larger rate than the control. Compared to short-term employment of the sulfide which was found a temporary solution addressing declined SAD rate during operating the PBR, applying sulfide for inoculation facilitated the formation of biofilm, leading to sustained improvement of SAD performance and better adaptation to coldness.