Bariloche protein symposium argentine society for biochemistry and molecular biology

75
BIOCELL, 27 (Suppl. I), 2003
MI-P62.
MANGANESE TRANSPORT EXPRESSION IN
Sinorhizobium meliloti
Platero, Raúl; Jaureguy, Melina and Fabiano, Elena.
Laboratorio de Ecología Microbiana, IIBCE, MEC, Unidad
Asociada a Facultad de Ciencias. Montevideo, Uruguay. E-mail:
[e-mail]
The intracellular concentration of transition metals such as Fe,
Mn, Co, Cd, Ni and Zn are precisely controlled through the
regulation of its transport across the membrane. Bacterial
manganese transport systems identified so far comprise: the Natural
Resistance-Associated Macrophage Protein (NRAMP)- type
transporters; the ABC-type transporters and the P-type ATPase
transporter found only in Lactobacillus plantarum. In the genome
of the symbiotic á-proteobacterium Sinorhizobium meliloti, genes
homologous to NRAMP and ABC type manganese transport
systems have been identified. In previous works we demonstrate
that the ABC type MntABCD system is involved in manganese
transport in S. meliloti. Bioinformatic studies have revealed a
putative  fur  (ferric  uptake  regulation)  gene at 122 bp from the
presumed mntA start codon in the complementary strand, and Fur
regulation of mntA  expression was studied. In order to evaluate
the expression of this transport system and to elucidate its relevance
during the symbiosis with alfalfa plants, transcriptional fusions
with the reporter gfp gene and the promoter regions of mntA and
fur genes were constructed. Nodules were harvested from plants
inoculated with S. meliloti cells carrying the gfp constructions.
Fluorescent microscopy of nodules showed that the mntA:gfp
construction was active suggesting a role for this transporter in
the symbiotic interaction. The expression of fur:gfp construction
is actually under study.
Supported by CSIC and PEDECIBA- Uruguay.
MI-P63.
CHARACTERIZATION OF Herbaspirillum seropedicae
MUTANTS RELATED TO IRON METABOLISM
Rosconi, Federico
1
; Platero, Raúl
2
; González, Marcela
2
; González,
Cecilia
1
; Batista, Silvia
1
; Gill, Paul R.
3
and Fabiano, Elena
2
.
1
Depto. Bioquímica and 
2
Lab. Ecología Microbiana, IIBCE
(Us.As. Fac. de Ciencias); 
3
Lab. Tecnología Molecular, Fac. de
Ciencias. Uruguay. E-mail: [e-mail]
Herbaspirillum seropedicae is a grass endophyte that belongs to
the 
β subgroup of proteobacteria. In association with some rice
cultivars, it is able to express nitrogenase and to promote plant
growth. Nitrogenase complex contains about 40 iron atoms
highlighting the importance of iron in this process. With the aim
to elucidate iron uptake systems in H. seropedicae and to evaluate
its contribution to the plant growth promotion, a generalized
mutagenesis was done with a minTtn5gus-o-gfp transposon.
Transconjugants screening was based on siderophore production
in CAS solid medium. Five mutants that accumulate siderophores
and twenty that did not produce halo in CAS plates were obtained.
The interrupted genes of three of those mutants presented high
homology with: exbD (a gene that encodes a component of the
TonB complex implicated in iron internalization), acnA (the gene
of aconitase A) and a putative gene for sulfite reductase (cysJI).
The gusA (
β-glucuronidase) gene present in the mini-transposon
was inserted in the same orientation of the interrupted genes. In
the ExbD
-
 mutant (which overproduce halo in CAS plates), gusA
was induced in cells grown on iron-chelated medium. The putative
mutants AcnA
- 
and CysJI
- 
did not produce halo in CAS plates. GUA
expression of cultures grown in different media was evaluated.
Supported by RITE-Japan.
MI-P64.
THE CGM GENE OF B. ABORTUS  ENCODES A
MEMBRANE PROTEIN THAT IS REQUIRED FOR
SUCCINYLATION OF CYCLIC 
β-1,2- GLUCAN
Roset, Mara S.; Ugalde, Rodolfo A. and Iñon de Iannino, Nora.
IIB-INTECH, UNSAM CONICET, Buenos Aires, Argentina.
E-mail: [e-mail]
Brucellae periplasmic cyclic 
β-1,2-glucan provides important
function during bacteria host interaction. In addition to the well-
characterized neutral cyclic glucan, periplasmic glucans contain
anionic components not previously reported. The presence of highly
substituted forms of the cyclic 
β-1,2-glucan may be important in
the Brucella infection process. In the present study, we describe
that the anionic cyclic 
β-1,2-glucan are substituted with succinyl
residues. We have identified a B. abortus 1.203-kb open reading
frame with 39% identity to Rhodobacter sphaeroides succinyl
transferase, named cgm for Cyclic Glucan Modifier. Cgm mutant
produces neutral glucans without succinyl residues, confirming
the identity of this protein as the B. abortus cyclic glucan succinyl
transferase. Despite the absence of subtituted in cyclic 
β-1,2-
glucan, mutant cgm was shown to effectively infect Balb/c mice,
indicating that substitution of cyclic 
β-1,2-glucans with succinyl
residues is not essential for Brucella infection.
MI-P65.
PHYLOGENETIC ANALYSIS OF ARGENTINEAN MUMPS
VIRUS ISOLATES
Rosana Rota
1
, Gabriel Iglesias
2
, Marcelo Argüelles
1
, Graciela
Glikmann
1
.
1
Lab. de Inmunología y Virología, 
2
Lab. de Microbiología, Univ.
Nac. de Quilmes. E-mail: [e-mail]
Mumps virus (MuV) is a member of the genus Rubulavirus in the
family Paramyxoviridae. The single-stranded genomic RNA
contains seven genes including the small hydrophobic (SH) gene,
which encodes a protein of 57 amino acids. This gene has been
used to genotype MuV strains, since it is the most variable portion
of the genome. Purified RNA specimens isolated from throat swabs
samples of acute mumps patients, confirmed by IgM capture ELISA
and collected between 1997 and 2000, were amplified by RT-PCR
using specific primers of the intergenic regions flanking the SH
gene. All samples were subjected to nucleotide sequence analysis.
Phylogenetic analysis of the sequences obtained and previously
published sequences from USA, Canada, Portugal, UK, France,
Germany, Switzerland, Denmark, Sweden, Russia, China and
Japan showed the existence of the 11 genotypes (A-J) described.
All the local strains studied belonged to genotype A, which also
includes some vaccine strains, like Enders and Jeryl Lynn. When
the deduced 57 amino acid sequences were analyzed the signature
sequence motifs specific of this genotype were identified, being
the amino acids at positions 28-30 the most characteristic motif.
The local isolates showed more than 95% of nucleotide identity
when compared with Enders and Jeryl Lynn strains and about 80%
with Urabe strain. These variations induced non-synonymous
changes at the amino acid level only when compared with Jeryl
Lynn and Urabe strains.

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