# Isolation and Properties of _Enterobacter_ sp. LX3
## 4 Discussion  
According to the description for the genus _Enterobacter_[24], these determinative phenotypic criteria were included: Gram-negative, motile by peritrichous flagella, facultative anaerobic rod, positive Voges-Proskauer reaction, negative test in methyl red reaction, no hydrolyzation of corn oil and tributyrin. Strain LX3 shared coincident key characteristics with genus _Enterobacter_ (Table 1) [24]. Thus, strain LX3 was phenotypically classified in the genus _Enterobacter_. Comparisons in 16S rRNA gene sequences between strain LX3 and its related genera also suggested that strain LX3 should be a member of the genus _Enterobacter_. Isolate LX3 showed more than 97.8% similarity to all species of genus _Enterobacter_ in 16S rRNA gene sequences. These data coincided with a proposal that 93% or 95% similarity was used as a cut-off value to delineate genera [25; 26]. As shown in the phylogenetic tree (Figure 2), strain LX3 has a close phylogenetic relationship with genus _Enterobacter_ species from tree topology. It was clear to cluster strain LX3 into clade of _E. cloace_ that had a 99.8% similarity, in which _Enterobacter_ sp. CCBAU15492 appears related to _E. cloace_[27]. Those phylogenetic results proved that strain LX3 must be part of genus _Enterobacter_. Strain LX3 coincided with the genus _Enterobacter_ in phenotypic characteristics, whereas there were some notable differences in biochemical traits at species level (Table 3). Such discrepancies should be significant to distinguish strain LX3 from other members of genus _Enterobacter_. The data in Table 3 showed a distinction between strain LX3 and its nearest apparent phylogenetic neighbors of genus _Enterobacter_ in a number of key characteristics, such as H\({}_{2}\)S production, indole production, urease, Voges-Proskauer reaction and enzyme activities including \(\beta\)-galactosidase, lysine decarboxylase and arginine dihydrolase. To distinguish strain LX3 from the most closely related _E. cloace_, decisive characteristics were lysine decarboxylase, \(\beta\)-galactosidase, urease, indole production and acid production from both d-mannitol and sucrose. _E. ludwigii_ can be distinguished from strain LX3 by urease test, indole production, lysine decarboxylase and \(\beta\)-galactosidase. Isolate LX3 also was differentiated from its closer neighbor _Leclercia aderboxylata_ in phenotypic properties, such as \(\beta\)-galactosidase, lysine decarboxylase, arginine dihydrolase and urease tests. Isolate LX3 showed positive lysine decarboxylase, but most of species in the genus _Enterobacter_ were deficient in lysine decarboxylase production except for _E. aerogenes_. Whereas _E. aerogenes_ showed difference from isolate LX3 in arginine dihydrolase activity, indole production and urease. Moreover, \(\beta\)-galactosidase could be detected in most of genus _Enterobacter_ species, but not in strain LX3 and _E. aerogenes_. Both strain LX3 and _E. tabaci_ were positive for indole production and Voges-Proskauer reaction, whereas _E. tabaci_ was positive in H\({}_{2}\)S production and strain LX3 was not. Contrary characteristics occurred between strain LX3 and _E. cancerogenus_, such as \(\beta\)-Galactosidase, lysine decarboxylase, urease and indole production. Being different from most species in the genus _Enterobacter_, both strain LX3 and _E. asburiae_ gave a positive result in urease test, in which discrepancy between strain LX3 and _E. asburiae_ occurred in indole production and Voges-Proskauer reaction. As shown in Table 3, some differences between isolate LX3 and genus _Enterobacter_ species also occurred in carbohydrate fermentation tests. Based on both phenotypic characteristics and phylogenetic analysis, isolate LX3 could be considered as a new species of the genus _Enterobacter_ that is closely related with _E. cloace_. A creation of new species was proposed in the genus _Enterobacter_ despite needing more detailed taxonomic works to finish classification.