duckweed, while in cattail, biodegradation likely played an important role.
Betaproteobacteria, Gammaproteobacteria, and Bacteroidetes were detected and
might have significant correlations with TCS degradation [118]. Even if these
studies did not document TCS metabolites, they identified bacterial genera with
the potential to contribute to TCS metabolism in CWs. Rhizospheric bacteria
Dechloromonas sp., Clostridium sp., the order Sphingobacteriales, and the
Cytophaga sp. identified in roots from Typha angustifolia were most probably
responsible for the rhizodegradation of IBU [42]. IBU accumulated in leaves and
was partially transformed to IBU carboxylic acid, 2-hydroxy IBU, and 1-hydroxy
IBU. Bacteria participating in the degradation of antibiotics were also identified.
Man and coworkers observed how sulfonamides inhibited some functional microorganisms related to the sulfur and nitrogen cycles in the rhizosphere of wetland
plants [107]. On the other hand, sulfonamides significantly enriched methylotrophs
with potential to degrade the antibiotics such as Methylosinus, Methylotenera,
Methylocaldum, and Methylomonas [107].
5.2 Endophytic Bacteria Can Enhance Degradation
of Pharmaceuticals in Plants
Endophytic bacteria have been found in intercellular space in root tissues but also in
the xylem and in the cytosol of some cells. Since much of pharmaceutical metabolism in plants takes place in the cytosol and xenobiotic’s ultimate fate is often
conjugation and storage of the conjugates in the vacuole, endophytic bacteria can
influence metabolic pathways with their enzymes involved in phase I reactions,
introducing new metabolites in the plant xenome. Although the endosphere is a
habitat with lower bacterial diversity than the rhizosphere, the presence and concentration of pharmaceuticals have shown effects also on the endophytic bacterial
diversity in legume species irrigated with reclaimed wastewater [108] and in CW
species exposed to pharmaceuticals [115, 117].
Specific endophytic bacterial groups are enriched after plant treatment with
pharmaceuticals. In Miscanthus x giganteus, 16S rRNA amplicon sequencing of
the endophytic bacterial community showed an enrichment of Actinobacteria after
treatment with sulfamethoxazole and DCF [106]. Cultivation-dependent techniques
revealed similar results, and some isolated strains (e.g., Microbacterium aoyamense
and Streptomyces curacoi with additional plant-growth promoting traits) were able
to degrade DCF and sulfamethoxazole in vitro [106]. Alphaproteobacteria
(Novosphingobium and Oligotropha) and Betaproteobacteria (Herminiimonas,
Methylophilus, Cupriavidus) were enriched in roots of Juncus acutus exposed to a
high concentration of bisphenol-A, metals (Zn, Ni, Cd), and pharmaceuticals (sulfamethoxazole and ciprofloxacin) pollution [115]. The work of Syranidou et al. is
one of the few studies using previously isolated endophytic strains for
bioaugmentation of CWs and shows how bacterial strains may improve the
Metabolism of Pharmaceuticals in Plants and Their Associated Microbiota
253
Betaproteobacteria, Gammaproteobacteria, and Bacteroidetes were detected and
might have significant correlations with TCS degradation [118]. Even if these
studies did not document TCS metabolites, they identified bacterial genera with
the potential to contribute to TCS metabolism in CWs. Rhizospheric bacteria
Dechloromonas sp., Clostridium sp., the order Sphingobacteriales, and the
Cytophaga sp. identified in roots from Typha angustifolia were most probably
responsible for the rhizodegradation of IBU [42]. IBU accumulated in leaves and
was partially transformed to IBU carboxylic acid, 2-hydroxy IBU, and 1-hydroxy
IBU. Bacteria participating in the degradation of antibiotics were also identified.
Man and coworkers observed how sulfonamides inhibited some functional microorganisms related to the sulfur and nitrogen cycles in the rhizosphere of wetland
plants [107]. On the other hand, sulfonamides significantly enriched methylotrophs
with potential to degrade the antibiotics such as Methylosinus, Methylotenera,
Methylocaldum, and Methylomonas [107].
5.2 Endophytic Bacteria Can Enhance Degradation
of Pharmaceuticals in Plants
Endophytic bacteria have been found in intercellular space in root tissues but also in
the xylem and in the cytosol of some cells. Since much of pharmaceutical metabolism in plants takes place in the cytosol and xenobiotic’s ultimate fate is often
conjugation and storage of the conjugates in the vacuole, endophytic bacteria can
influence metabolic pathways with their enzymes involved in phase I reactions,
introducing new metabolites in the plant xenome. Although the endosphere is a
habitat with lower bacterial diversity than the rhizosphere, the presence and concentration of pharmaceuticals have shown effects also on the endophytic bacterial
diversity in legume species irrigated with reclaimed wastewater [108] and in CW
species exposed to pharmaceuticals [115, 117].
Specific endophytic bacterial groups are enriched after plant treatment with
pharmaceuticals. In Miscanthus x giganteus, 16S rRNA amplicon sequencing of
the endophytic bacterial community showed an enrichment of Actinobacteria after
treatment with sulfamethoxazole and DCF [106]. Cultivation-dependent techniques
revealed similar results, and some isolated strains (e.g., Microbacterium aoyamense
and Streptomyces curacoi with additional plant-growth promoting traits) were able
to degrade DCF and sulfamethoxazole in vitro [106]. Alphaproteobacteria
(Novosphingobium and Oligotropha) and Betaproteobacteria (Herminiimonas,
Methylophilus, Cupriavidus) were enriched in roots of Juncus acutus exposed to a
high concentration of bisphenol-A, metals (Zn, Ni, Cd), and pharmaceuticals (sulfamethoxazole and ciprofloxacin) pollution [115]. The work of Syranidou et al. is
one of the few studies using previously isolated endophytic strains for
bioaugmentation of CWs and shows how bacterial strains may improve the
Metabolism of Pharmaceuticals in Plants and Their Associated Microbiota
253