Université Cheikh Anta Diop, Dakar, BP 5005, Sénégal
3Laboratoire de Microbiologie des Sols,
IRD/ISRA/UCAD, B.P. 1386, Dakar, Sénégal
*Corresponding author; e-mail:
In this review, we discuss the recent progress in research on
symbiotic association of rhizobia, Frankia and fungi with plant
roots. We compare infection processes of symbiotic establishment;
structure, functioning and molecular biology of the symbiotic
organ including the regulation of genes implicated in rhizobial,
actinorhizial and arbuscular mycorhizal symbioses.
Key words: Symbiosis, nodule, mycorrhiza, symbiotic
genes.
Effects of mixed nitrogen sources on biodegradation of
phenol by immobilized Acinetobacter sp.
strain W-17
Desouky Abd-El-Haleem1*,
Usama Beshay1, Abdou O.
Abdelhamid 2, Hassan
Moawad3 and Sahar Zaki1
1Environmental Biotechnology Department &
Bioprocess Development Department, Genetic Engineering and
Biotechnology Research Institute (GEBRI), Mubarak City for
Scientific Research and Technology Applications, New Burg-Elarab
City, Alexandria, Egypt.
2Chemistry Department, Faculty of Science, Cairo
University, Cairo, Egypt.
3Agricultural Microbiology Department, National
Research Centre, Dokki, Cairo, Egypt.
*Corresponding author; e-mail:
Using Ca-alginate immobilized cells of Acinetobacter sp.
strain W-17, the effects of ammonium-N and nitrate-N on the biodegradation
of phenol were investigated. Degradation experiments in
three different culture media; minimal salts medium (MSM),
simulated (SW) and modified simulated wastewater (MSW) were
performed. With the freely suspended cells (cell dry weight 0.2
g/l), complete phenol (500 mg/l) degradation was achieved after
incubation for 120 h. Using the immobilized cells, the time was
reduced to 24 h in MSM medium, and 15 h in the MSW. The results
also indicate that strain W-17 can tolerate to high
concentrations of NH4+-N (63 mg/l) and NO3--N
(1000 mg/l) without a significant loss in the phenol
biodegradation rate. Moreover, the presence of 500 mg/l phenol in
the MSW had no considerable effect on the removal of both
ammonium-N and nitrate-N. Repeated use of immobilized cells
revealed that they could be used as much as five times without
loss of activity. Our findings could be extended to enhance
biotreatment of phenol contamination in a variety of biological
treatment processes.
Key words: Phenol, biodegradation, immobilization, Acinetobacter,
Ca-alginate, ammonium, nitrate.
Diversity of indigeneous bradyrhizobia associated with
three cowpea cultivars (Vigna unguiculata
(L.) Walp.) grown under limited and favorable water conditions in
Senegal (West Africa)
Tatiana Krasova-Wade1,
2, *, Ibrahima Ndoye1,
2, Serge Braconnier3,
Benoit Sarr3, Philippe de
Lajudie4 and Marc Neyra1
1Laboratoire de Microbiologie, IRD, BP 1386, Dakar,
Senegal
2Département de Biologie Végétale, Université
Cheikh Anta Diop, BP 5005, Dakar, Senegal
3Centre d'Etude Régional pour l'Amélioration de
l'Adaptation à la Sécheresse (CERAAS), BP 3320, Thiès Escale,
Thies
4Laboratoire des Symbioses Tropicales et
Méditerranéennes (LSTM), Campus de Baillarguet, TA10/J, 34398
Montpellier Cedex 5, France
*Corresponding author; phone: (221) 849 33 19, fax: (221) 832 16
75, e-mail:
The diversity of Bradyrhizobium strains nodulating three
cowpea (Vigna unguiculata L. Walp.) cultivars in favorable and
water-limited conditions occuring at flowering was analysed. PCR-
Restriction Fragment Length Polymorphism (PCR-RFLP) analysis of
16S-23S rDNA intergenic spacer region (IGS) directly applied on
85 crushed nodules distinguished four genetic profiles, IGS types
I, II, III and IV. The distribution of these IGS types according
to water conditions and cowpea cultivars (B-21, TN 88-63 and
Mouride) showed that nodulating strains appeared more diverse in
water-limited condition. More than three quarters of prospected
nodules presented the IGS type I. They were formed on all three
cultivars and in both water conditions. Only a small part of
nodules was distributed between the IGS type II, III and IV.
Nodules showing the IGS types II and III were found mainly in
limited conditions on TN 88-63 and Mouride cultivars, whereas
nodules presenting the IGS type IV were collected only from
cultivars B-21 and Mouride, in both water conditions. Strains
corresponding to the different profiles were isolated. The
phylogenetic analysis of 16S rRNA gene sequences showed that they
belong to the genus, Bradyrhizobium. The sequence analysis of
16S-23S rDNA IGS revealed that the strains exhibiting IGS types
II, III and IV were closely related to some Faidherbia albida
isolates from Senegal. IGS type II can be assigned with at least
98% similarity to Bradyrhizobium genospecies IV. IGS types III
and IV showed more than 96% similarity with genospecies VII and
could belong to the same genospecies. IGS type I, the most
frequent, exhibits low IGS similarity with reported sequences in
the databases, and could represent a new genospecies.
Key words: Bradyrhizobium, Vigna unguiculata,
water-limited condition, PCR-RFLP, 16S rDNA, 16S-23S rDNA IGS.
Pre-harvest deterioration of Sour sop (Annona
muricata) at Ibadan Southwestern Nigeria and its
effect on nutrient composition
N. A. Amusa*, O. A. Ashaye, M. O. Oladapo and O.O.
Kafaru
Institute of Agricultural Research and Training Obafemi,
Awolowo University Moor Plantation PMB 5029 Ibadan, Nigeria
*Corresponding author; e-mail:
The etiology of pre-harvest deterioration of Soursop (Annona
muricata) fruit in Ibadan, southwestern Nigeria and the
effects on its nutrient composition was investigated. Four fungal
pathogens including Botryodiplodia theobromae, Fusarium
sp., Rhizopus stolonifer and Aspergillus niger
were found associated with the pre-harvest deteriorating soursop
. B. theobromae was the most prevalent and the most
pathogenic inducing rot of 75 mm in diameter within four days of
inoculation. There was a remarkable reduction in carbohydrate and
protein contents of the fungal infected fruits while all other
nutrients and mineral assayed were higher in the infected fruits
than the non-infected ones.
Key words: Annona muricata, fungal pathogens,
pre-harvest deterioration.