Isolation Of Antagonistic Bacteria Research Articles

Isolation of antagonistic bacteria from chickpea rhizosphere (Cicer arietinum L.)

Isolation of antagonistic bacteria from chickpea rhizosphere (Cicer arietinum L.)

Characterization of Host-Associated Microbiota and Isolation of Antagonistic Bacteria from Greater Amberjack (Seriola dumerili, Risso, 1810) Larvae.

Greater amberjack (Seriola dumerili) is a new species in marine aquaculture with high mortalities at the larval stages. The microbiota of amberjack larvae was analyzed using 16S rDNA sequencing in two groups, one added copepod nauplii (Acartia tonsa) in the diet, and one without copepods (control). In addition, antagonistic bacteria were isolated from amberjack larvae and live food cultures. Proteobacteria was the most abundant phylum followed by Bacteroidota in amberjack larvae. The composition and diversity of the microbiota were influenced by age, but not by diet. Microbial community richness and diversity significantly increased over time. Rhodobacteraceae was the most dominant family followed by Vibrionaceae, which showed the highest relative abundance in larvae from the control group 31 days after hatching. Alcaligenes and Thalassobius genera exhibited a significantly higher relative abundance in the copepod group. Sixty-two antagonistic bacterial strains were isolated and screened for their ability to inhibit four fish pathogens (Aeromonas veronii, Vibrio harveyi, V. anguillarum, V. alginolyticus) using a double-layer test. Phaeobacter gallaeciensis, Phaeobacter sp., Ruegeria sp., and Rhodobacter sp. isolated from larvae and Artemia sp. inhibited the fish pathogens. These antagonistic bacteria could be used as host-derived probiotics to improve the growth and survival of the greater amberjack larvae.

MicroMundo Upside Down: Targeted Searching for Antibiotics-Producing Bacteria From Soil With Reverse Antibiosis Approaches.

Tiny Earth (TE) is a popular international citizen science program aimed at improving public awareness on the growing antimicrobial resistance problem of which MicroMundo Albacete is a Spanish node. With a protocol that is focused on the isolation of antibiotics-producing actinomycetes from soil, 70% of the high school students in MicroMundo Albacete 2020 isolated colonies with antagonistic activity against Gram-positive tester bacteria. However, no activity was found against Gram-negative bacteria. Here, we further adapted the protocol toward a more targeted screening that also enables isolation of antagonistic bacteria against Gram negatives using two different reverse-antibiosis approaches involving a spraying technique or flipping soil sample disks upside down. Exploiting the soil samples from MicroMundo Albacete 2020, the new approaches yielded isolation of actinomycete bacteria with antagonistic activity against Gram-negative as well as Gram-positive tester bacteria. We propose that (educational) science programs which aim to search for antibiotic-producing bacteria may implement these approaches in their protocol to promote a successful and stimulating outcome of the experiment for the participating students.

Inhibitory effect of bacterial antagonists on the growth of Macrophomina phaseolina (Tassi.) Goid. Causing charcoal rot of sunflower (Helianthus annus L.) invitro

Charcoal rot caused by Macrophominaphaseolinais a major disease causing in sunflower plant. The pathogen invasion occurs from the seedling to maturity stage. To overcome this problem in vitro, sensitivity of M. phaseolina was determined through inhibition zone technique to various isolates of antagonistic bacteria like seven isolates of Pseudomonas fluorescens (EPf2, EDPf3, APf4, CPf5, MPf6, KPf7 and Pf1)and seven isolates Bacillus subtilis (EBs1, EDBs2, ABs3, CBs4, MBs5, KBs6 and Bs10) amended into PDA medium. The results showed that the entire bacterial antagonist were effective against the fungus M. phaseolina and exhibited appreciable amount of inhibition. Among these bacterial antagonist significantly compared to the control P.fluorescens (Pf1) proved to be the most effective (71.49 %) with an inhibition zone of 5.00 mm reducing the colony growth of M. Phaseolina followed B. subtilis (65.92 %)inhibition zone of 17.80 mm respectively over control. However, from these studies it is concluded that an isolate of various antagonist can vary in its sclerotia producing ability on root.

Antagonistic bacteria in the soil after cover crops cultivation

The purpose of the studies was to establish the quantitative composition of bacteria Bacillus spp. and Pseudomonas spp. and their antagonistic effect towards soil-borne fungi after the cultivation of oats, spring vetch and tansy phacelia as intercrop cover plants. The total population of bacteria in 1 g dry weight of the soil from the experimental combination where mulch of oats was used was larger than in the combination with spring vetch or tansy phacelia. Totally, approximately three times as much Bacillus spp. was obtained from soil samples as compared to Pseudomonas spp. Tests showed that the most isolates of antagonistic bacteria out of the enumerated genera occurred in the soil after oats cultivation, and the least in the soil after the cultivation of tansy phacelia. Antagonistic Bacillus spp. and Pseudomonas spp. inhibited the growth and development of Fusarium oxysporum, Haematonectria haematococca and Thanatephorus cucumeris in the most effective way. The greatest total antagonistic effect of Bacillus spp. and Pseudomonas spp. towards Altenaria alternata, F. culmorum, F. oxysporum, H. haematococca, P. irregulare and T. cucumeris was found out after managing the mulch of oats. The smallest total antagonistic effect of bacteria was observed after managing the mulch of tansy phacelia.

In Vitro Evaluation of Antagonistic Microorganisms for the Control of Die-Back of Neem Causal Agent Phomopsis Azadirachtae

In VitroEvaluation of Antagonistic Microorganisms for the Control of Die-Back of Neem Causal AgentPhomopsis AzadirachtaeThe die-back of neem caused byPhomopsis azadirachtaeis a devastating disease in India reducing the life span and seed production of neem. Six isolates of antagonistic bacteria and fungi,Bacillus cereus(MTCC 430),B. subtilis(MTCC 619),Pseudomonas aeruginosa(MTCC 2581),P. oleovorans(MTCC 617),Trichoderma harzianum(MTCC 792) andT. viride(MTCC 800) were evaluated againstP. azadirachtaeunderin vitroconditions. Culture filtrates of all these microorganisms were extracted using ethyl acetate, and the obtained fractions were tested for their antifungal activity againstP. azadirachtaeat different concentrations. Ethyl acetate extracts ofB. subtilisandP. aeruginosawere highly effective and completely inhibited the growth ofP. azadirachtaeat 25 ppm concentration. Both these isolates may be considered as factors for the biological control of die-back of neem.

イネもみ枯細菌病菌による苗腐敗症の発病条件と拮抗微生物の分離

イネもみ枯細菌病菌による苗腐敗症の発病条件と拮抗微生物の分離

Biological Control of Sheath Blight Disease of Rice by using Antagonistic Bacteria

The study was made to detect and identify antagonistic bacteria to control Rhizoctonia solani, a causal organism of sheath blight (ShB) disease of rice. Isolation of antagonistic bacteria was done from ShB infected rice leaf collected from the districts of Gazipur, Rajshahi, Bogra and Comilla. Fifty isolates of bacteria were isolated. These isolates were tested for antagonism against ShB pathogen of in PDA medium. Among the isolates of antagonistic bacteria (both fluorescent and non fluorescent), eleven produced more than 15 mm inhibition zone, were selected for this study. Remarkable inhibition zone producing ten isolates were selected to observe their antagonistic behaviour by soaking the sclerotia of Rhizoctonia solani and rice seedlings in different hours into bacterial suspension of 3.84 x 107 CFU/ml. Both the in vitro and in vivo rom showed that the sclerotial germination and sheath blight symptom expression were delayed 6-9 days. Soaking of both seedlings and sclerotia with the test bacteria was found most effective to control ShB (38% - 100%) than soaking of seedlings alone with bacterial suspension at different hours. However, BanShbFPS5 (2)B, BanShb738(3), BanShb738(2) and BanShb581(1), the four antagonistic bacterial isolates could be applied as biological agent to control sheath blight disease of rice and they could control sheath blight disease development and could delay the epidemics of the disease. Key words: Biological control; Sheath blight disease; Rhizoctonia solani; Antagonistic bacteria DOI: 10.3329/bjsir.v45i3.6529Bangladesh J. Sci. Ind. Res. 45(3), 225-232, 2010