Members of a new molecular family of bacterial nonspecific acid phosphatases (NSAPs), indicated as class C, were found to share significant sequence similarities to bacterial class B NSAPs and to some plant acid phosphatases, representing the first example of a family of bacterial NSAPs that has a relatively close eukaryotic counterpart. Despite the lack of an overall similarity, conserved sequence motifs were also identified among the above enzyme families (class B and class C bacterial NSAPs, and related plant phosphatases) and several other families of phosphohydrolases, including bacterial phosphoglycolate phosphatases, histidinol‐phosphatase domains of the bacterial bifunctional enzymes imidazole‐glycerolphosphate dehydratases, and bacterial, eukaryotic, and archaeal phosphoserine phosphatases and threalose‐6‐phosphatases. These conserved motifs are clustered within two domains, separated by a variable spacer region, according to the pattern [FILMAVT]‐D‐[ILFRMVY]‐D‐[GSNDE]‐[TV]‐[ILVAM]‐[ATS VILMC]‐X‐{YFWHKR}‐X‐{YFWHNQ}‐X( 102, 191 )‐{KRHNQ}‐G‐D‐{FYWHILVMC}‐{QNH}‐{FWYGP}‐D‐{PSNQYW}. The dephosphorylating activity common to all these proteins supports the definition of this phosphatase motif and the inclusion of these enzymes into a superfamily of phosphohydrolases that we propose to indicate as “DDDD” after the presence of the four invariant aspartate residues. Database searches retrieved various hypothetical proteins of unknown function containing this or similar motifs, for which a phosphohydrolase activity could be hypothesized.

Antibiotic resistance, evolving and spreading among bacterial pathogens, poses a serious threat to human health. Antibiotic use for clinical, veterinary and agricultural practices provides the major selective pressure for emergence and persistence of acquired resistance determinants. However, resistance has also been found in the absence of antibiotic exposure, such as in bacteria from wildlife, raising a question about the mechanisms of emergence and persistence of resistant strains under similar conditions, and the implications for resistance control strategies. Since previous studies yielded some contrasting results, possibly due to differences in the ecological landscapes of the studied wildlife, we further investigated this issue in wildlife from a remote setting of the Galapagos archipelago. Screening for acquired antibiotic resistance was carried out in commensal enterobacteria from Conolophus pallidus, the terrestrial iguana of Isla Santa Fe, where: i) the abiotic conditions ensure to microbes good survival possibilities in the environment; ii) the animal density and their habits favour microbial circulation between individuals; and iii) there is no history of antibiotic exposure and the impact of humans and introduced animal species is minimal except for restricted areas. Results revealed that acquired antibiotic resistance traits were exceedingly rare among bacteria, occurring only as non-dominant strains from an area of minor human impact. Where both the exposure to antibiotics and the anthropic pressure are minimal, acquired antibiotic resistance traits are not normally found in bacteria from wildlife, even if the ecological landscape is highly favourable to bacterial circulation among animals. Monitoring antibiotic resistance in wildlife from remote areas could also be a useful tool to evaluate the impact of anthropic pressure.

Eleven environmental samples from different sources were screened for the presence of metallo-β-lactamase-producing bacteria by using a selective enrichment medium containing a carbapenem antibiotic and subsequently testing each isolate for production of EDTA-inhibitable carbapenemase activity. A total of 15 metallo-β-lactamase-producing isolates, including 10Stenotrophomonas maltophiliaisolates, 3Chryseobacteriumspp., oneAeromonas hydrophilaisolate, and oneJanthinobacterium lividumisolate (a species in which production of metallo-β-lactamase activity was not previously reported), were obtained from 8 samples. In theJ. lividumisolate, named JAC1, production of metallo-β-lactamase activity was elicited upon exposure to β-lactams. Screening of a JAC1 genomic library for clones showing a reduced imipenem susceptibility led to the isolation of a metallo-β-lactamase determinant encoding a new member (named THIN-B) of the highly divergent subclass B3 lineage of metallo-β-lactamases. THIN-B is most closely related (35.6% identical residues) to the L1 enzyme ofS. maltophiliaand more distantly related to the FEZ-1 enzyme ofLegionella gormanii(27.8% identity) and to the GOB-1 enzyme ofChryseobacterium meningosepticum(24.2% identity). Sequences related tobla_THIN-B, and inducible production of metallo-β-lactamase activity, were also detected in theJ. lividumtype strain DSM1522. Expression of thebla_THIN-Bgene inEscherichia coliresulted in decreased susceptibility to several β-lactams, including penicillins, cephalosporins (including cephamycins and oxyimino cephalosporins), and carbapenems, revealing a broad substrate specificity of the enzyme. The results of this study indicated that metallo-β-lactamase-producing bacteria are widespread in the environment and identified a new molecular class B enzyme in the environmental speciesJ. lividum.