Effect of unsaturated fatty acids in growth inhibition of some penicillin-resistant and sensitive bacteria

The growth of two penicillin-resistant Gram-positive bacteria, Bacillus licheniformis (749/C, penicillin G-resistant) and Staphylococcus aureus (metR 18, methicillin-resistant) and one Gram-negative strain, Escherichia coli (cloxacillin-resistant) as well as that of their wild counterparts was inhibited by the long-chain unsaturated fatty acids, linoleic, linolenic and arachidonic acid. The minimum inhibitory concentrations (MIC) of all the fatty acids were found to be 4–6 μg/ml for Staph. aureus (metR 18 & wild), 8–30 μg/ml for B. licheniformis (749/C & wild) and 70–90 μg/ml for E. coli (cloxacillin-resistant & wild). The inhibitory activity increased as the number of double bonds in the fatty acids increased. In most instances the concentrations of fatty acids required to inhibit the growth of the penicillin-resistant strains were lower than that required for their sensitive counterparts. This inhibition of growth in the presence of fatty acids may be due to an increase in permeability of the membrane as evidenced by the measurement of the leakage of 260 nm absorbing material and fluidity.     

Incorporation of monoclonal antibodies into cells by osmotic permeabilization. Effect on cellular metabolism

Incorporation of asparagine synthetase-specific monoclonal antibodies into L5178Y D10/R (L-asparaginase-resistant) murine lymphoma cells by osmotic lysis of pinocytic vesicles was used to evaluate the potential of the technique for macromolecular incorporation for metabolic studies. Nonspecific effects of the incorporation procedure included temporary inhibition of protein and DNA synthesis by 80-85% and a transitory loss of membrane integrity. Cells incorporated with an antibody inhibitory to tumor cell asparagine synthetase showed increased dependence upon an exogenous source of asparagine in the culture medium, while cells incorporated with a control antibody were not affected. These studies demonstrated that incorporation of inhibitory monoclonal antibodies into cells can be used to study the short term metabolic role of specific enzymes; however, the metabolic effects induced by the specific macromolecule must be evaluated within the context of the nonspecific effects caused by the osmotic treatment required for incorporation.     

Interaction of metal ions with carboxylic and carboxamide groups in protein structures

An analysis of the geometry of metal binding by carboxylic and carboxamide groups in proteins is presented. Most of the ligands are from aspartic and glutamic acid side chains. Water molecules bound to carboxylate anions are known to interact with oxygen lone-pairs. However, metal ions are also found to approach the carboxylate group along the C-O direction. More metal ions are found to be along the syn than the anti lone-pair direction. This seems to be the result of the stability of the five-membered ring that is formed by the carboxylate anion hydrogen bonded to a ligand water molecule and the metal ion in the syn position. Ligand residues are usually from the helix, turn or regions with no regular secondary structure. Because of the steric interactions associated with bringing all the ligands around a metal center, a calcium ion can bind only near the ends of a helix; a metal, like zinc, with a low coordination number, can bind anywhere in the helix. Based on the analysis of the positions of water molecules in the metal coordination sphere, the sequence of the EF hand (a calcium-binding structure) is discussed.     

Biomineralization of 2,3,4,6-Tetrachlorophenol by Bacillus sp. and Staphylococcus sp. Isolated from Secondary Sludge of Pulp and Paper Mill

Three 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)-mineralizing bacteria were isolated from the secondary sludge of a pulp and paper industry. The isolates used 2,3,4,6-TeCP as a source of carbon and energy and were capable of degrading this compound, as indicated by stoichiometric release of chloride and biomass formation. Based on 16S rRNA gene sequence analysis, the bacteria were identified as Bacillus megaterium (CL3), Staphylococcus suciri (CL10), and Bacillus thuringensis (CL11). High-performance liquid chromatography (HPLC) analysis revealed that these isolates were able to degrade 2,3,4,6-TeCP at higher concentrations (600 mg/L or 2.5 mM). A consortia of the isolates completely removed 2,3,4,6-TeCP from the sludge obtained from a pulp and paper mill within 2 weeks when supplemented at a rate of 100 mg/L or 0.43 mM. A bacterial consortium also significantly reduced absorbable organic halogen (AOX) and extractable organic halogen (EOX) by 63% and 68%, respectively, from the sludge. These isolates have a high potential to remove 2,3,4,6-TeCP and may be used for remediation of pulp paper mill waste containing 2,3,4,6-TeCP.