TABLE 1.
Screening of endophytic bacteria and related strains for their metabolic properties and functions that affect plant hormone balances and growtha
| Metabolic property or functionb | OD660 of:
|
||||||
|---|---|---|---|---|---|---|---|
| 568 | 638 | Bu61 | Bu72 | W619 | R551-3 | BJ001 | |
| Autotrophy | − | − | − | − | − | − | − |
| Nitrogen fixation | − | − | − | − | − | − | − |
| d-Mannitol | +++ | ++ | ++ | +++ | +++ | ++ | +++ |
| Lactose | + | +++ | − | − | − | − | − |
| Sucrose | ++ | + | ++ | ++ | +++ | + | ++ |
| Arbutin | +++c | ++ | −c | ++ | +++c | + | ++ |
| Salicin | ++ | + | − | +++ | ++ | ++ | ++ |
| Pectin | − | − | − | +/− | − | − | − |
| Trehalose | +++ | ++ | − | +++ | ++ | − | ++ |
| d-Mannose | ++ | + | +++ | ++ | ++ | ++ | ++ |
| l-Arabinose | ++ | ++ | +++ | +++ | ++ | − | ++ |
| Xylose | − | ++ | +++ | ++ | ++ | + | ++ |
| Maltose | + | ++ | − | − | ++ | +/− | ++ |
| Cellobiose | ++ | ++ | − | ++ | ++ | − | ++ |
| Chitin | + | +/− | ++ | ++ | ++ | ++ | ++ |
| GABA | ++ | − | +++ | +++ | ++d | − | ++ |
| PAA | ++ | − | +++ | +++ | ++e | − | − |
| ACC | − | − | + | + | − | − | − |
| Glucose | ++ | + | +++ | ++ | ++ | + | + |
| Gluconate | +++ | ++ | +++ | ++ | +++ | +++ | ++ |
The endophytic bacteria S. proteamaculans 568, Enterobacter strain 638, B. cepacia Bu72, P. putida W619, S. maltophilia R551-3, and M. populi BJ001 and the soil bacterium B. vietnamiensis Bu61 were tested for their metabolic properties. Cultures were inoculated at OD660 of 0.01. Growth of the cultures was determined by an increase of OD660, which was followed until the cultures had reached stationary growth phase or after 5 days. +++, OD660 of >0.8; ++, OD660 of 0.5 to 0.8; +, OD660 of 0.25 to 0.5; +/−, OD660 of 0.1 to 0.25; −, OD660 of <0.1. Experiments were carried out as independent triplicates.
Autotrophy or nitrogen fixation was tested by growing the strains on minimal growth medium that lacked a carbon or nitrogen source, respectively. ACC deaminase activity (ACC) was determined by testing the growth on 1-aminocyclopropane-1-carboxylic acid as either a carbon or nitrogen source. GABA and PAA metabolism were determined by testing bacterial growth on these compounds as either a carbon or nitrogen source. The IAA concentrations produced by strains 568, 638, Bu61, Bu72, W619, R551-3, and BJ001 were 3.23, 3.90, 2.57, 2.38, 29.39, 2.98, and 9.38 μg/ml, respectively. These concentrations were determined using the method of Salkowski (17) and calculated for a culture OD660 of 1.0.
Brown color formation in the medium.
Orange color formation in the medium.
Yellow color formation in the medium.