Isolation and Screening of Zinc and Potassium Solubilizing Microorganisms from Different Rhizospheric Soil

Zinc is considered as a crucial trace micronutrient for proper growth, reproduction and driving of many metabolic reactions in all crops. Potassium is classified as a macronutrient associated with movement of water and nutrients as well as enzyme activation. The present study was aimed for isolation and screening of zinc and potassium solubilizing microorganisms from different rhizospheric soil of rice. Eight different isolates- ZSB1, ZSB2, ZSB3, ZSB4, KSB1, KSB2, KSB3 and KSB4 were obtained and were screened for their Zinc and Potassium solubilizing activities on TRIS minimal agar medium and Aleksandrov’s medium, respectively. Upon characterization, ZSB1, ZSB4 and KSB3 were observed as motile Gram-negative organisms, ZSB2, KSB2 and KSB4 as motile Gram-positive organisms while ZSB3 and KSB1 had mycelial growth with some conidial spore. All isolates gave positive results for starch and lipid hydrolysis. In gelatin hydrolysis, only ZSB3, ZSB4, KSB1 and KSB2 gave positive results. The main purpose to obtain these zinc and potassium solubilizing microorganisms was for their use in plant growth promotion as biofertilizers to increase soil fertility and crop yield.

Biochemical and Molecular Analysis ofStaphylococcus aureusClinical Isolates from Hospitalized Patients

Staphylococcus aureusis opportunistic human as well as animal pathogen that causes a variety of diseases. A total of 100Staphylococcus aureusisolates were obtained from clinical samples derived from hospitalized patients. The presumptiveStaphylococcus aureusclinical isolates were identified phenotypically by different biochemical tests. Molecular identification was done by PCR using species specific 16S rRNA primer pairs and finally 100 isolates were found to be positive asStaphylococcus aureus. Screened isolates were further analyzed by several microbiological diagnostics tests including gelatin hydrolysis, protease, and lipase tests. It was found that 78%, 81%, and 51% isolates were positive for gelatin hydrolysis, protease, and lipase activities, respectively. Antibiogram analysis of isolatedStaphylococcus aureusstrains with respect to different antimicrobial agents revealed resistance pattern ranging from 57 to 96%. Our study also shows 70% strains to be MRSA, 54.3% as VRSA, and 54.3% as both MRSA and VRSA. All the identified isolates were subjected to detection ofmecA,nuc, andhlbgenes and 70%, 84%, and 40% were found to harbourmecA,nuc, andhlbgenes, respectively. The current investigation is highly important and informative for the high level multidrug resistantStaphylococcus aureusinfections inclusive also of methicillin and vancomycin.

Disease of Floral Buds of Kiwifruit in Spain Caused by Pseudomonas syringae

In 1999 and 2000, decay of floral buds of Actinidia deliciosa was observed in plantations in the Principality of Asturias, Spain. Bud decay led to a decrease (up to 40%) in the production of kiwifruit. Floral buds with symptoms of browning and necrosis were collected from different areas (Villaviciosa, Grado, and Pravia) and processed for microbiological analysis. A fluorescent bacterium was recovered on King's B medium and identified as Pseudomonas syringae by the LOPAT scheme and Hugh-Leifson reaction (2). Other biochemical features included esculin and gelatin hydrolysis and acid production from mannitol, erythritol, sorbitol, and m-inositol, which are features associated with P. syringae (2). Three isolates from different samples were selected to test pathogenicity using Koch's postulates. Overnight broth cultures of each isolate (109 CFU/ml) were used to infect A. deliciosa in the trials by the following procedures: (i) atomization on branches and buds; (ii) bud injection (1 ml in each bud); and (iii) bud cutting with a scalpel dipped in the suspension. Branches and buds inoculated with sterile water were used as controls. The inoculated parts were enclosed in plastic bags for 48 h. Assays were repeated at least twice. Disease symptoms appeared 2 days later, initially as dark brown spots that developed into an extensive bud rot in all inoculated cases, while no symptoms occurred in controls. P. syringae was successfully recovered from infected samples but not from control samples. The data support the pathogenicity of P. syringae on A. deliciosa. Although P. syringae was previously reported in Italy as the causal agent of disease on floral buds of A. deliciosa (1), to our knowledge, this is the first report of infection of kiwifruit by this pathogen in Spain. References: (1) G. M. Balestra and L. Varvaro. J. Phytopathol. 145:375, 1997. (2) MAPA, Manual de laboratorio, MAPA, Madrid, Spain, 1991.

Aminopeptidase activities inPeptostreptococcusspp. are statistically correlated to gelatin hydrolysis

One hundred Peptostreptococcus isolates from five species were assessed for their ability to hydrolyze gelatin. Most Peptostreptococcus magnus (95.8%) and Peptostreptococcus micros isolates (79.0%) hydrolyzed gelatin in contrast to Peptostreptococcus asaccharolyticus (8.0%), Peptostreptococcus anaerobius (10.0%), and Peptostreptococcus prevotii isolates (16.7%). Gelatin hydrolysis in Peptostreptococcus magnus and Peptostreptococcus micros isolates correlated (r = 0.80; P = 0.0019) with more aminopeptidases produced than Peptostreptococcus asaccharolyticus, Peptostreptococcus anaerobius, or Peptostreptococcus prevotii. The five species were further classified into three groups using the extended Tukey test (P < 0.0001) based on the mean percentage of aminopeptidases produced by each species with Peptostreptococcus magnus and Peptostreptococcus micros belonging to group I, Peptostreptococcus asaccharolyticus and Peptostreptococcus prevotii belonging to group II, and Peptostreptococcus anaerobius forming group III. An analysis of possible proteolytic activity of four selected Peptostreptococcus magnus isolates indicated that only 5 of 11 substrates were hydrolyzed as compared to a control isolate of Porphyromonas gingivalis W83, which had a strong proteolytic profile. Therefore, gelatin hydrolysis by Peptostreptococcus spp., in particular Peptostreptococcus magnus and Peptostreptococcus micros, is probably due to a variety of aminopeptidases rather than proteinases.Key words: Peptostreptococcus, aminopeptidases, proteolytic activity.