Authors:C. Elliott, Z. Ye, S. Mojumdar, and M. Saleh
One of the limiting factors to the effectiveness of biostimulation and bioremediation is the loss of inoculated material from
the site. This can occur by a number of pathways, but is particularly problematic in open water systems where the inoculated
material is simply lost in the water. It is desirable to develop new material, a matrix, within which bacteria and/or biostimulants
can be incorporated.
We have investigated the basic physical properties of insoluble potato starch to eventually evaluate its use as such a matrix.
Insoluble starch fibers were prepared from white potato (Solanum tuberosum) and sweet potato (Ipomoea batatas) and were compared for their melting temperature by DSC and their ability to bind/aggregate bacteria. The DSC curves for
white and sweet potato showed that the melting temperature is 127.34 and 133.05�C for white and sweet potato fibers, respectively.
The TG curves for white and sweet potato starches exhibited one main mass loss step corresponding to the DTG peak temperature
at 323.39 and 346.93�C, respectively. The two types of fibers, however, showed different binding/aggregation capacities for
bacteria, with white potato approximately twice as many cells of Burkholderia cepacia (22.6 billion/g) as cells of Pseudomonas putida. The reverse was true for fibers from sweet potato, binding twice as many cells of Pseudomonas putida (23 billion/g) as cells of Burkholderia cepacia.
Authors:Samantha Pitt, Ágnes Vehovszky, Henriette Szabó, and C. J. H. Elliott
We describe octopamine responses of 3 large buccal neurons of Lymnaea and test the hypothesis that these are cAMP-dependent. The B1 neuron is excited by octopamine and the depolarisation is significantly enlarged (P<0.05) by application of the blocker of cAMP breakdown, 3-isobutyl-1-methylxanthine (IBMX). The B1 neuron is also depolarised by forskolin, an activator of adenylyl cyclase. The B2 and B3 neurons are inhibited by octopamine, and the response is not affected by IBMX. Both cells are excited by forskolin. We conclude that the B1 neuron response to octopamine is likely to be mediated by cAMP, while the B2 and B3 responses are cAMP-independent.
Authors:Ágnes Vehovszky, A. Szűcs, Henriette Szabó, Samantha Pitt, and C. J. H. Elliott
Octopamine is released by the intrinsic OC interneurons in the paired buccal ganglia and serves both as a neurotransmitter and a neuromodulator in the central feeding network of the pond snail Lymnaea stagnalis . The identified B1 buccal motoneuron receives excitatory inputs from the OC interneurons and is more excitable in the presence of 10 mM octopamine in the bath. This modulatory effect of octopamine on the B1 motoneuron was studied using the two electrode voltage clamp method. In normal physiological saline depolarising voltage steps from the holding potential of -80 mV evoke a transient inward current, presumably carried by Na+ ions. The peak values of this inward current are increased in the presence of 10 mM octopamine in the bath. In contrast, both the transient (IA) and delayed (IK) outward currents are unaffected by octopamine application. Replacing the normal saline with a Na+-free bathing solution containing K+ channel blockers (50 mM TEACl, 4 mM 4AP) revealed the presence of an additional inward current of the B1 neurons, carried by Ca2+. Octopamine (10 mM) in the bath decreased the amplitudes of this current. These results suggest that the membrane mechanisms which underlie the modulatory effect of octopamine on the B1 motoneuron include selective changes of the Na+- and Ca2+-channels.