normalized to the optical density at day 0 for the appropriate cell type. Growth curve was determined twice

Growth curves were prepared for various cell lines using the modified method adopted by Serrano et al, 1997. Briefly, 10, 000 cells were seeded in a 24 well plate in quadruples. At the indicated times, cells were washed once with PBS and fixed in 10% formalin for 20 minutes and rinsed with distilled water. Cells were stained with 0.05% crystal violet for 30 minutes, rinsed extensively and dried. Cell associated dye was extracted with 1.0ml acetic acid. Aliquots were diluted 1:4 with water and transferred to 96 well microtitre plates and the optical density at 590nm determined. Values were

Growth Curves:

Polyphosphates from yeast cells were extracted with phenol-chloroform solutionas described previously(Neefand Kladde,2003). Cells grown eitherovernight or to logarithmic phase in YPDmediumwere harvested by centrifugation at 1,700 rpm for 5 min. Cells were washed with 10 ml sterile MQ water and resuspendedin ice-cold 500 μl20%trichloro acetic acid (TCA) solution to the final cell densityof 100 OD. Cell suspension was transferred toa1.5 ml microcentrifuge tube. After incubation at room temperature for 5 min, cells were harvested by centrifugation at 12,000 g for 10 minat 4 ̊C and resuspendedin 250-350 μlpolyphosphate extraction buffer.Equal volume of phenol-chloroform (25:24) was addedtothe microcentrifuge tube and aqueous phase was extracted by centrifugation at 12,000 g for 8 minat room temperature. Top aqueous layer was collected with a 200 μl tip. Aqueous layer extraction was repeated once more after removal of DNA with chloroform.After centrifugation,aqueous phasecontaining RNA and polyphosphates wascollected,RNA was quantified at A260nmandstored at -20 ̊C

Polyphosphate extraction

For RNA experiments, all solutions were prepared in RNase free diethylpyrocarbonate (DEPC) water. Microcentrifuge tubes and tips used for RNAworkwere autoclaved twice and driedat 70 ̊C for overnight before use. Non-autoclavable plastic items were wiped with Ambion RNAseZap to remove RNAse contamination, if any. RNA was extracted from C.glabrata cells usingacid phenol extraction method. C. glabratacells were harvested at 2,500g for 5 minat 4 ̊C, resuspended in 1 ml ice-cold DEPC water and were transferred toa2 ml microcentrifuge tube. Cells were spun down at 6,000g for 3 minat 4 ̊C and resuspended in 350 μl AE solution. Next, 50 μl SDS and 400 μl acid phenol(pH 4.5)solutions were added to thetube and mixed well by vortexing. The tube wasincubated at 65 ̊C for 15 min with continuous mixing. After incubation, tube was kept on ice for 5 minand centrifuged at 7,500g for 5 minat 4 ̊C. Aqueous phase was transferred toa new 1.5 ml microcentrifuge tube and RNAwasextracted with an equal volume of chloroform. Total RNA was precipitated at room temperature with 1/10thvolume of 3 M sodium acetate (pH 5.2) and 2.5 volumesof chilledabsolute ethanol for 20 min. Precipitated RNA was collected by centrifugation at 7,500g for 5 minat 4 ̊C. RNA pellet was washed with chilled 70% ethanol and resuspended in 50 μl nuclease-free water. RNA concentration was determined by measuring absorbance at 260 nm. Quality of extracted RNA was examined by gel electrophoresis on 0.8% agarose gel prepared in DEPC-treated TAE buffer

RNA extraction

Intracellular iron content in different Xanthomonas oryzaepv. oryzicolastrains was measured by using atomic absorption spectroscopy as described previously with few modifications (Velayudhan et al., 2000). For estimation of intracellular iron, different strains of Xanthomonas oryzaepv. oryzicolawere grown overnight in 3 ml PS media with appropriate antibiotics for differentially marked strains. 0.2% of the overnight grown culture was inoculated in 250 ml PS medium alone or PS plus 2, 2’-dipyridyl for iron stravation, and grown to an OD600 of 1.2. Cells were then pelleted down by centrifuging at 7000 g for 10 min, and washed twice with phosphate buffer saline (PBS). After washing, cells were lyophilized, and their dry weights were determined. Lyophilized cells were then dissolved in 30% nitric acid at 80ºC for 12 h and diluted 10-fold with miliQ water. Iron content was determined by atomicabsorption spectroscopy using ICP-OES (JY 2000 sequential Inductively Coupled Plasma Optical Emisson spectrometer,Jobin Yvon, Horiba, France). Iron level was quantified against aqueous standard of iron traceable to NIST (National institute of standards and technology, India)

Estimation of intracellular iron content

PCR-positive transformants were inoculated in 10 ml YPD medium, allowedto grow for 12 handgenomic DNAwas isolated.Another round of PCR was performed using genomic DNA asatemplate toconfirm the gene deletion

A homologous recombination-based strategy was used to disrupt C. glabraraORFs witha cassette containing the nat1gene, which codes for nourseothricin acetyltransferase and imparts resistance to nourseothricin. Briefly, 5’-and 3’-UTR region (nearly 500-700 bp) of the gene to be deleted were amplified by PCR using wild-type genomic DNA as template. Both 5’-and 3’-UTR amplified products were fused to one half each ofthenat1gene amplified from theplasmid(pRK625). The two nat1-amplified fragments share about 300-350 bp complimentary region. To obtain fusion products, primers were designed insucha way thatthereverse primer for 5’-UTR and the forward primer for 3’-UTRof the gene of interestshare 20 bp complimentary region with the forwardprimer for 5’nat1fragment andthereverse primer for 3’nat1fragment amplification, respectively. The fused PCR products were co-transformed in to the wild-type strain and transformants were plated on YPD-agar plates. Plates were incubated at 30°C for 16 h to allow the homologous recombination between nat1fragments,and 5’-and 3’-UTR atthegenomic loci. Post incubation,cells were replica plated ontoYPD-agar plate supplemented with 200 μg/ml nourseothricin and incubated for another 24 h. Nourseothricin-resistant colonies were purified and verified for gene disruption viahomologous recombination by PCR using appropriate set of primers

Generation of C. glabratadeletion strains

PCR-positive transformants were inoculated in 10 ml YPD medium, allowedto grow for 12 handgenomic DNAwas isolated.Another round of PCR was performed using genomic DNA asatemplate toconfirm the gene deletion

A homologous recombination-based strategy was used to disrupt C. glabraraORFs witha cassette containing the nat1gene, which codes for nourseothricin acetyltransferase and imparts resistance to nourseothricin. Briefly, 5’-and 3’-UTR region (nearly 500-700 bp) of the gene to be deleted were amplified by PCR using wild-type genomic DNA as template. Both 5’-and 3’-UTR amplified products were fused to one half each ofthenat1gene amplified from theplasmid(pRK625). The two nat1-amplified fragments share about 300-350 bp complimentary region. To obtain fusion products, primers were designed insucha way thatthereverse primer for 5’-UTR and the forward primer for 3’-UTRof the gene of interestshare 20 bp complimentary region with the forwardprimer for 5’nat1fragment andthereverse primer for 3’nat1fragment amplification, respectively. The fused PCR products were co-transformed in to the wild-type strain and transformants were plated on YPD-agar plates. Plates were incubated at 30°C for 16 h to allow the homologous recombination between nat1fragments,and 5’-and 3’-UTR atthegenomic loci. Post incubation,cells were replica plated ontoYPD-agar plate supplemented with 200 μg/ml nourseothricin and incubated for another 24 h. Nourseothricin-resistant colonies were purified and verified for gene disruption viahomologous recombination by PCR using appropriate set of primers

Generation of C. glabratadeletion strains