“
Ca.
Nitrotoga” is a NOB of high environmental relevance, but physiological data exist for only a few representatives. Initially, it was detected in specialized niches of low temperature and low nitrite concentrations, but later on, its ubiquitous distribution revealed its critical role for N removal in engineered systems like WWTPs. In this study, we analyzed the competition between
Nitrotoga
and
Nitrospira
in bioreactors and identified conditions where the
K
strategist
Ns. defluvii
was almost replaced by
Nitrotoga
sp. BS. We show that the pH value is an important factor that regulates the composition of the nitrite-oxidizing enrichment with a dominance of
Nitrotoga
sp. BS versus
Ns. defluvii
at a neutral pH of 7.4 in combination with a temperature of 17°C. The physiological diversity of novel
Nitrotoga
cultures improves our knowledge about niche differentiation of NOB with regard to functional nitrification under suboptimal conditions.
As one group of the most important functional phosphorus removal organisms, “
Candidatus
Accumulibacter,” affiliated with the
Rhodocyclus
group of the
Betaproteobacteria
, is a widely recognized and studied PAO in the field of biological wastewater treatment. The morphotypes and population structure of clade-level “
Candidatus
Accumulibacter” were studied through novel FISH-staining-flow cytometry, which involved denitrifying phosphorus removal (DPR) achieving carbon and energy savings and simultaneous removal of N and P, thus inferring the different denitrifying phosphorus removal abilities of these clades. Additionally, based on this method,
in situ
quantification for specific polyphosphate-accumulating organisms (PAOs) enables a more efficient process and more accurate result. The establishment of FISH-staining-flow cytometry makes cell sorting of clade-level noncultivated organisms available.
Coconut is an important crop for both industry and small stakeholders in many intertropical countries. Phytoplasma-associated lethal yellowing-like diseases have become one of the major pests that limit coconut cultivation as they have emerged in different parts of the world. We developed a multilocus sequence typing scheme (MLST) for tracking epidemics of “
Ca
. Phytoplasma palmicola,” which is responsible for coconut lethal yellowing disease (CLYD) on the African continent. MLST analysis applied to diseased coconut samples collected in western and eastern African countries also showed the existence of three distinct populations of “
Ca
. Phytoplasma palmicola” with low intrapopulation diversity. The reasons for the observed strong geographic patterns remain to be established but could result from the lethality of CLYD and the dominance of short-distance insect-mediated transmission.