# Isolation and Properties of _Enterobacter_ sp. LX3
## 3 Results
### Phenotypic Characteristics  
Isolate LX3 grew well at 37 \({}^{\circ}\)C but could not hydrolyze corn oil and tributyrin (Table 1). A positive catalase test was achieved but a negative oxidase test was observed. Isolate LX3 gave positive results on enzyme activities including arginine dihydrolase, lysine decarboxylase and ornithine decarboxylase,  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Characteristics** & **Strain LX3** & **Characteristics** & **Strain LX3** \\ \hline Gram stain & \(-\) & Voges-Proskauer reaction & \(+\) \\ Straight rod & \(+\) & Methyl red & \(-\) \\ Endospore formation & \(-\) & Nitrate reduction & \(+\) \\ Motility & \(+\) & Tetrathionate reduction & \(-\) \\ Facultative anaerobic & \(+\) & Corn oil and tributyrin hydrolysis & \(-\) \\ \(\beta\)-Galactosidase & \(-\) & Alkaline reaction in Simmons citrate & \(+\) \\ Argin dihydrolase & \(+\) & Citrate as sole carbon/energy source & \(+\) \\ Lysine decarboxylase & \(+\) & Acid and gas production from glucose & \(+\) \\ Ornithine decarboxylase & \(+\) & Gas production from glucose at 44.5 \({}^{\circ}\)C & \(-\) \\ Phenylalanine deaminase & \(-\) & Acid production from: & \\ Catalase & \(+\) & d-Glucose & \(+\) \\ Oxidase & \(-\) & d-Mannitol & \(-\) \\ Urease & \(+\) & Inositol & \(-\) \\ Acid fast & \(-\) & d-Sorbitol & \(+\) \\ Gelatin liquefaction & \(-\) & l-Rhamnose & \(+\) \\ Esculin hydrolysis & \(+\) & Sucrose & \(-\) \\ Growth at 37 \({}^{\circ}\)C & \(+\) & Melibiose & \(+\) \\ H\({}_{2}\)S production & \(-\) & Arabinose & \(+\) \\ Indole production & \(+\) & Amygdala & \(+\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Phenotypic characteristics of the newly isolated _Enterobacter_ sp. LX3. Symbols: \(+\), 90% or more strains were positive; \(-\), 10% or less strains were positive.  
Figure 1: Screening of indoleacetic acid (IAA)-producing strains isolated from the maize rhizosphere soil collected from Shenyang Agricultural University, China, in which colony 66 is strain LX3. Error bars were calculated by standard deviations from triplicate runs for IAA production assay. Different letters on top of bars indicate significant differences (\(p<0.05\)).  
but negative results on enzyme activities of \(\beta\)-galactosidase and phenylalanine deaminase. Glucose was fermented to produce both acid and gas at 30 \({}^{\circ}\)C but gas was not produced at 44.5 \({}^{\circ}\)C. Isolate LX3 was negative in testing hydrogen sulfide production but positive in testing indole production. Isolate LX3 also gave a positive result on Voges-Proskauer reaction but negative test in methyl red reaction. Gelatin was liquefied and esculin was hydrolyzed. Acid was produced from compounds: Amygdala, arabinose, d-glucose, d-sorbitol, l-thannose and melibiose. No acid production was detected from compounds including d-mannitol, inositol and sucrose. Nitrate could be reduced into nitrite and tetrathionate could not be reduced. Positive alkaline reaction was detected in Simmons citrate broth.  
Strain LX3 could utilize many carbohydrates including cellobiose, d-glucose, d-fructose, d-galactose, d-mannose, lactose, l-arabinose, l-rhamnose, maltose, melibiose, raffinose, sucrose, trehalose, d-mannitol, d-sorbitol and inositol as the sole carbon and energy source. A good growth was observed in the medium when yeast extract, peptone, tryptone, diammonium phosphate or ammonium sulfate were utilized as nitrogen sources. Strain LX3 could grow with citrate as sole carbon and energy source. It was not halophilic but able to grow in the medium containing 4% NaCl.  
Isolate LX3 was capable of growing at pH range from 5.0 to 9.0, and optimum pH for cell growth was at pH 7.0. Cell growing temperature for strain LX3 was between 20 \({}^{\circ}\)C and 45 \({}^{\circ}\)C, and the maximal cell growth was observed at temperature of 30 \({}^{\circ}\)C.