Influence of Triton X-100 on growth of Pseudomonas putida No. 69-3, an n-heptanol-tolerant variant of an organic solvent-sensitive bacterium, Pseudomonas putida No. 69

 When Pseudomonas putida No. 69-3 cells, changed as an organic solvent-resistant variant from an organic solvent-sensitive parent, Pseudomonas putida No. 69, were cultivated with 0.01% surfactants, Triton X-100 provided the highest cell growth in the presence of 10% n-heptanol. When strain No. 69-3 was cultivated in a medium containing 10% n-heptanol and various concentrations of Triton X-100, 0.01% Triton X-100 gave the most improved cell growth. Hydrophobicity of the cell membrane did not change in the presence or absence of Triton X-100. However, when strain No. 69-3 was cultivated in a medium containing 0.01% Triton X-100 or without Triton X-100 and the culture broth was centrifuged at 500×g, the decrease in optical density of the supernatant was smaller when the cells were cultivated in a medium containing 0.01% Triton X-100 than when cultivated without Triton X-100. This result suggests that Triton X-100 decreased the degree of aggregation and improved growth. Received: 15 May 1998 / Accepted: 30 September 1998     

Continuous pollution monitoring using Photobacterium phosphoreum

Photobacterium phosphoreum is a marine bacterium which is used extensively as a bioluminescent indicator of pollutants, where the presence of toxicants diminishes light output. To evaluate the utility of cell immobilisation in continuous toxicity testing, the sensitivity of P. phosphoreum to five gelling agents was evaluated relative to the retention of bioluminescence in 3% NaCl-glycerol suspensions. Following storage at 4°C, the control cultures retained light output for up to 2 weeks before significant decline; alginate-glycerol suspensions were stable for up to 4 weeks and bioluminescence was detectable for up to 6 weeks. Cells stored in agar were no more stable than the control, whereas cells gelled in agarose and low-melting point agarose showed a significant decline in bioluminescence within 2 weeks of storage. Bioluminescence was totally retained in alginate-glycerol suspensions stored at −80°C for up to 12 weeks. P. phosphoreum was successfully immobilised in strontium alginate and showed a dose-related response to four of the five heavy metal ions, SDS and pentachlorophenol tested when responses were followed over a time-course. A flow-through system for Sr-alginate immobilised cells was developed and conditions for operation were optimised. When cells were exposed to a pulse of 4-nitrophenol or salicylate then the nutrient feed continued, bioluminescence declined in response (pulse of 4–6 min) to these pollutants then recovered to a new stable rate of decline which was faster than the pre-exposure rate. These results demonstrate the potential of using immobilised P. phosphoreum in a continuous flow-through system for real-time environmental monitoring of water quality.     

Responses of herbaceous mimosa (Mimosa strigillosa), a new reclamation species, to soil pH

Growth responses of herbaceous mimosa (Mimosa strigillosa Torr. and Gray), a potential new reclamation species in the SE USA and Mexico, to nine soil pH scales were studied under a controlled environment at Nacogdoches, TX, USA. Twenty seeds were planted in each of 40 (nine scales plus one control in four replicates) 20.3-cm pots filled with Tonkawa sandy soil. These pots were treated with H₂SO₄ or Ca(OH)₂ to adjust each pot to its designated pH level. After 15 days of seeding, the emergence rate was at best about 50–70% for pH 4.7–6.6. The plant can survive and grow at soil pH as low as 4.7, but the optimum growth seems to be on soils with pH ranging from 6.2 to 7.1. At this pH range, the plant exhibits higher values of green and dry biomass, longer shoot growth and lower root/shoot weight and length ratios. The survival rate was greater than 90% for all treatments, except for pH 4.1. There were no nutrient deficiencies in plant tissues on soil pH 4.7 or higher. The plant allocated more growth to the shoot under optimum conditions, but more growth to the roots under environmental stress. It is not suitable for herbaceous mimosa to grow on soils with pH 4.1 or less.     

Responses of herbaceous mimosa (Mimosa strigillosa), a new reclamation species, to cyclic moisture stress

A greenhouse study was conducted to evaluate the response of herbaceous mimosa (Mimosa strigillosa) to six levels of cyclic soil moisture stresses in a 17-week period. The results showed that the cultivar continued to grow and the biomass continued to increase even when the soil moisture stress was as high as at the wilting point (1500 Kpa). Also, transpiration recovery rate was quick and values of root/shoot ratio were high when the plant was subject to the cyclic moisture stress condition. All these characteristics, along with strong rooting and spreading ability, suggest this legume as a promising drought hardiness species for reclamation purposes.