16S rDNA studies on members of Arthrobacter and Micrococcus: An aid for their future taxonomic restructing

Abstract 16S rDNA sequence data was obtained for 11 species of Arthrobacter and 4 species of Micrococcus and compared with that from other members of the arthrobacterial lineage within the order Actinomycetales . The intermixing of members of these two genera and the placement of Renibacterium salmoninarum within the radiation of these two genera, as previously suggested by 16S rRNA cataloguing, is confirmed. The branching pattern reveals several closely related organisms that cluster around the type species of Arthrobacter and Micrococcus ; these species are considered 'core organisms'. A few species, however, branch outside the radiation of core organisms; these include Micrococcus kristinae, Micrococcus halophilus , and, as previously indicated, Micrococcus sedentarius and M. nishinomiyaensis . As phenotypic data that would support the exclusion of these four species from the genus Micrococcus are still lacking taxonomic conclusions should await more thorough comparative studies.     

Synthesis and characterization of gold nanoparticles from marine Micrococcus sp. OUS9

Studies on biological synthesis techniques of nanoparticles have been significantly expanded in recent years. This reduced adverse effects of chemical processing techniques. We describe the synthesis and characterization of gold nanoparticles from marine Micrococcus sp. OUS9 for potential application in nanobiotechnology.     

Stabilization of Micrococcus lysodeikticus cells towards lysis by lysozyme using glutaraldehyde: application as a novel biospecific ligand for the purification of lysozyme

Micrococcus lysodeiekticus was stabilized against the lytic action of lysozyme by cross-linking with 5% (v/v) glutaraldehyde for 24 h but still retained its ability to bind lysozyme. An immobilized, biospecific ligand was prepared by covalently binding the cells to glutaraldehyde activated amino-Sepharose followed by stabilization of the cells with glutaraldehyde. Lysozyme bound specifically to this column and could be eluted by glycine/NaOH buffer (50 mM, pH 10.0) containing 2 M KCl.     

The sandfly Lutzomyia longipalpis shows specific humoral responses to bacterial challenge

Abstract The presence of immune molecules induced by microorganisms in the haemolymph of Lutzomyia longipalpis sandflies has been investigated. Injections of Escherichia coli and Micrococcus luteus into female sandflies induced anti-bacterial activity in the haemolymph. Inhibition zone assays showed that haemolymph from E.coli and M.luteus injected sandflies differentially inhibited M.luteus growth. This differential effect was specific to M. luteus infection since anti-Zs. coli activity was similar in haemolymph from both E.coli oxM.luteus injected sandflies. Haemolymph following injection of either bacteria showed the induction of a 4kDa peptide. Haemolymph from M.luteus injected sandflies also contained a 33 kDa polypeptide which was absent in haemolymph from E.coli and control uninfected insects. Sandflies, in common with other insects, were shown to possess general and specific humoral immune responses to the presence of microorganisms.     

Optimization of medium for the production of a novel aquaculture probiotic,<Emphasis Type="Italic">Micrococcus</Emphasis> MCCB 104 using central composite design

A marine isolate ofMicrococcus MCCB 104 has been identified as an aquaculture probiotic antagonistic toVibrio. In the present study different carbon and nitrogen sources and growth factors in a mineral base medium were optimized for enhanced biomass production and antagonistic activity against the target pathogen,Vibrio harveyi, following response surface methodology (RSM). Accordingly the minimum and maximum limits of the selected variables were determined and a set of fifty experiments programmed employing central composite design (CCD) of RSM for the final optimization. The response surface plots of biomass showed similar pattern with that of antagonistic activity, which indicated a strong correlation between the biomass and antagonism. The optimum concentration of the carbon sources, nitrogen sources, and growth factors for both biomass and antagonistic activity were glucose (17.4 g/L), lactose (17 g/L), sodium chloride (16.9 g/L). ammonium chloride (3.3 g/L), and mineral salts solution (18.3 mL/L).     

Purification and properties of diaminopimelate decarboxylase ofMicrococcus glutamicus

Diaminopimelate decarboxylase (EC 4.1.1.20) ofMicrococcus glutamicus ATCC 13059 was purified to homogeneity. The enzyme had an apparent molecular weight of 191,000 as determined by gel filtration on Sephadex G-200. At protein concentrations of 20 and 10 μg per ml and in the absence of pyridoxal-5′-phosphate, it dissociated into a species of molecular weight 94,000. The polypeptide chain molecular weight as determined by sodium dodecyl sulphate Polyacrylamide gel electrophoresis was 100,000. TheK _m formeso diaminopimelate was 0.5 mM and that for pyridoxal-5′-phosphate was 0.6 μI. Sulphydryl groups and pyridoxal-5′-phosphate were essential for activity and stability. The enzyme was inhibited significantly by L-lysine and DL-aspartic β-semialdehyde.     

Excretion of lysine byMicrococcus glutamicus

Analysis of intracellular and extracellular lysine concentration during lysine fermentation byMicrococcus glutamicus AEC RN-13-6/1 indicated that lysine excretion occurs against a concentration gradient towards the end of the fermentation period. The capacity to excrete lysine against a concentration gradient may be a factor contributing to the high yield of lysine.