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Purple phototrophic bacteria are outcompeted by aerobic heterotrophs in the presence of oxygen
Water Research ( IF 12.8 ) Pub Date : 2021-02-18 , DOI: 10.1016/j.watres.2021.116941
Gabriel Capson-Tojo , Shengli Lin , Damien J. Batstone , Tim Hülsen

There is an ongoing debate around the effect of microaerobic/aerobic conditions on the wastewater treatment performance and stability of enriched purple phototrophic bacteria (PPB) cultures. It is well known that oxygen-induced oxidative conditions inhibit the synthesis of light harvesting complexes, required for photoheterotrophy. However, in applied research, several publications have reported efficient wastewater treatment at high dissolved oxygen (DO) levels. This study evaluated the impact of different DO concentrations (0-0.25 mg·L−1, 0-0.5 mg·L−1 and 0-4.5 mg·L−1) on the COD, nitrogen and phosphorus removal performances, the biomass yields, and the final microbial communities of PPB-enriched cultures, treating real wastewaters (domestic and poultry processing wastewater). The results show that the presence of oxygen suppressed photoheterotrophic growth, which led to a complete pigment and colour loss in a matter of 20-30 h after starting the batch. Under aerobic conditions, chemoheterotrophy was the dominant catabolic pathway, with wastewater treatment performances similar to those achieved in common aerobic reactors, rather than those corresponding to phototrophic systems (i.e. considerable total COD decrease (45-57% aerobically vs. ± 10% anaerobically). This includes faster consumption of COD and nutrients, lower nutrient removal efficiencies (50-58% vs. 72-99% for NH4+-N), lower COD:N:P substrate ratios (100:4.5-5.0:0.4-0.8 vs. 100:6.7-12:0.9-1.2), and lower apparent biomass yields (0.15-0.31 vs. 0.8-1.2 g CODbiomass·g CODremoved−1)). The suppression of photoheterotrophy inevitably resulted in a reduction of the relative PPB abundances in all the aerated tests (below 20% at the end of the tests), as PPB lost their main competitive advantage against competing aerobic heterotrophic microbes. This was explained by the lower aerobic PPB growth rates (2.4 d−1 at 35 °C) when compared to common growth rates for aerobic heterotrophs (6.0 d−1 at 20 °C). Therefore, PPB effectively outcompete other microbes under illuminated-anaerobic conditions, but not under aerobic or even micro-aerobic conditions, as shown by continuously aerated tests controlled at undetectable DO levels. While their aerobic heterotrophic capabilities provide some resilience, at non-sterile conditions PPB cannot dominate when growing chemoheterotrophically, and will be outcompeted.



中文翻译:

紫色光养细菌在氧气存在下被有氧异养菌所竞争

关于好氧/好氧条件对废水处理性能和浓缩紫色光养细菌(PPB)培养物稳定性的影响,目前正在进行辩论。众所周知,氧诱导的氧化条件抑制了光异养所需的光收集复合物的合成。然而,在应用研究中,一些出版物报道了在高溶解氧(DO)水平下的有效废水处理。本研究评价不同浓度DO的影响(0-0.25毫克·L -1,0-0.5毫克·L -1和0-4.5毫克·L -1)处理实际废水(家庭和家禽加工废水)时,其COD,氮和磷的去除性能,生物量产量以及富含PPB的培养物的最终微生物群落。结果表明,氧气的存在抑制了光异养生长,这导致在开始批处理后约20-30小时内颜料和颜色完全消失。在有氧条件下,化学趋化作用是主要的分解代谢途径,其废水处理性能与普通有氧反应器相似,而不是与光养系统相对应的废水处理性能(总COD降低(需氧量为45-57%vs.±10%厌氧)。这包括更快地消耗COD和养分,降低养分去除效率(50-58%,NH 4 + -N72-99%),较低的COD:N:P底物比率(100:4.5-5.0:0.4-0.8100:6.7-12:0.9-1.2相比)和更低的表观生物量产量(0.15-0.310.8-1.2 g COD生物量·g g COD去除-1))。在所有充气测试中,光合肥的抑制不可避免地导致相对PPB丰度降低(测试结束时低于20%),因为PPB失去了与竞争性需氧异养微生物的主要竞争优势。有氧PPB的生长速度较低(2.4 d -1与有氧异养菌的常见生长速度(20°C下6.0 d -1)相比时。因此,PPB在光照-厌氧条件下有效地胜过其他微生物,但在有氧甚至微需氧条件下却不能胜过其他微生物,如控制在不可检测的DO水平下的连续曝气测试所示。尽管它们的有氧异养能力提供一定的适应性,但在非无菌条件下,PPB在化学营养生长时不能占主导地位,并且将被淘汰。

更新日期:2021-02-26
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