Microbiologyhttp://repository.kln.ac.lk/handle/123456789/37492024-03-29T09:44:00Z2024-03-29T09:44:00ZPectobacterium carotovorum Phage vB_PcaM_P7_Pc Is a New Member of the Genus CertrevirusNaligama, K. N.Halmillawewa, A. P.http://repository.kln.ac.lk/handle/123456789/261202023-04-27T04:44:06Z2022-01-01T00:00:00ZPectobacterium carotovorum Phage vB_PcaM_P7_Pc Is a New Member of the Genus Certrevirus
Naligama, K. N.; Halmillawewa, A. P.
Pectobacterium carotovorum is an economically important phytopathogen
and has been identified as the major causative agent of bacterial soft rot in carrots.
Control of this phytopathogen is vital to minimizing carrot harvest losses. As fully effi-
cient control measures to successfully avoid the disease are unavailable, the phage-
mediated biocontrol of the pathogen has recently gained scientific attention. In this
study, we present a comprehensive characterization of the P. carotovorum phage
vB_PcaM_P7_Pc (abbreviated as P7_Pc) that was isolated from infected carrot samples
with characteristic soft rot symptoms, which were obtained from storage facilities at
market places in Gampaha District, Sri Lanka. P7_Pc is a myovirus, and it exhibits
growth characteristics of an exclusively lytic life cycle. It showed visible lysis against
four of the tested P. carotovorum strains and one Pectobacterium aroidearum strain.
This phage also showed a longer latent period (125 min) than other related phages;
however, this did not affect its high phage titter (.1010 PFU/mL). The final assembled
genome of P7_Pc is 147,299 bp in length with a G1C content of 50.34%. Of the 298
predicted open reading frames (ORFs) of the genome of P7_Pc, putative functions
were assigned to 53 ORFs. Seven tRNA-coding genes were predicted in the genome,
while the genome lacked any major genes coding for lysogeny-related products, con-
firming its virulent nature. The P7_Pc genome shares 96.12% and 95.74% average nu-
cleotide identities with Cronobacter phages CR8 and PBES02, respectively. Phylogenetic
and phylogenomic analyses of the genome revealed that P7_Pc clusters well within the
clade with the members representing the genus Certrevirus. Currently, there are only 4
characterized Pectobacterium phages (P. atrosepticum phages phiTE and CB7 and
Pectobacterium phages DU_PP_I and DU_PP_IV) that are classified under the genus,
making the phage P7_Pc the first reported member of the genus isolated using the
host bacterium P. carotovorum. The results of this study provide a detailed characteriza-
tion of the phage P7_Pc, enabling its careful classification into the genus Certrevirus.
The knowledge gathered on the phage based on the shared biology of the genus will
further aid in the future selection of phage P7_Pc as a biocontrol agent.
2022-01-01T00:00:00ZPectobacterium spp. isolated from rotting carrots obtained from markets in Gampaha district, Sri Lanka exhibit the potential of having broad host rangesNaligama, K.N.Halmillawewa, A.P.http://repository.kln.ac.lk/handle/123456789/254562022-11-01T06:33:15Z2022-01-01T00:00:00ZPectobacterium spp. isolated from rotting carrots obtained from markets in Gampaha district, Sri Lanka exhibit the potential of having broad host ranges
Naligama, K.N.; Halmillawewa, A.P.
Carrot production in Sri Lanka faces severe
post-harvest losses due to bacterial soft rot. The quality
deterioration of vegetables owing to typical bacterial soft
rot can greatly affect the market value and consumer
preference. Although the carrot soft rot causing bacteria
occur all over the world, and are well-studied and characterized,
the scarcity of data on the precise identification
of the causal agents of the disease in Sri Lanka acts as a
great barrier in managing such post-harvest losses. In an
attempt to bridge this knowledge gap, we have isolated
potential causative agents of bacterial soft rot from diseased
carrot samples collected from Gampaha district,
Sri Lanka.All the seven bacterial isolateswere confirmed
for their ability to exhibit pectolysis, and vegetable disk
assays were used to evaluate the pathogenicity of bacterial
isolates. The pathogenicity assays showed that these
isolates have the ability to infect not only carrot, but also
potato, radish, beetroot and Napa cabbage, suggesting
their possible broad host range. The ITS–PCR RELP
profiles of the pectobacterial isolates and hierarchical
clustering of the resulting profiles have placed the strains
isolated in this study into four groups. The 16S rRNA
gene sequencing and subsequent analyses aided in identifying
isolates as Pectobacterium carotovorum (C1B5,
C2B6, C2B7 and C2B8), P. aroidearum (C1B3 and
C1B4), and P. polaris (C3B9). The study indicated the
possibility of different Pectobacterium spp. being involved
in causing carrot soft rot in the area, emphasizing
the need to carry out an island-wide, comprehensive
analysis to understand the distribution of the pathogen,
which could be used in implementing successful disease
management strategies.
2022-01-01T00:00:00ZPhenotypic and genotypic characterization of antibiotic resistance of Listeria monocytogenes isolated from raw milk samples collected from Polonnaruwa, Sri LankaHarshani, H.B.C.Ramesh, R.Halmillawewa, A.P.Wijendra, W.A.S.http://repository.kln.ac.lk/handle/123456789/254522022-11-01T06:03:22Z2022-01-01T00:00:00ZPhenotypic and genotypic characterization of antibiotic resistance of Listeria monocytogenes isolated from raw milk samples collected from Polonnaruwa, Sri Lanka
Harshani, H.B.C.; Ramesh, R.; Halmillawewa, A.P.; Wijendra, W.A.S.
Listeria monocytogenes is a food-borne pathogen that can cause severe invasive infection called ‘listerosis’ in humans. Development of antibiotic resistance is a major setback in the management of conditions caused by Listeria in both human and veterinary medicine. In this study, antibiotic resistance of fifty L. monocytogenes strains isolated from raw milk samples collected from farms in Polonnaruwa district, Sri Lanka was determined for four commonly used antibiotics; penicillin, ampicillin, streptomycin and tetracycline. The strains were also tested for the presence of selected antibiotic resistant genes (penA, ampC, strA, strB, tetA and tetB). L monocytogenes isolates showed resistance to ampicillin (60%), penicillin (40%) streptomycin (16%) and tetracycline (8%) in diffusion assays. Phenotypic multidrug resistance was exhibited by twenty isolates. The tetracycline resistant gene (tetA) was detected in seven isolates, while tetB was not detected in any. Presence of streptomycin resistant genes (strA or strB) was confirmed in seven isolates. Ampicillin (ampC) and penicillin (penA) resistant genes were not detected in any of the tested isolates. Except from the samples collected from Sungavila area, isolates from other sampling areas showed resistance to at least one of the antibiotics tested, suggesting that raw milk samples are prone to be contaminated with L. monocytogenes strains with different antibiotic resistant profiles. Therefore, necessary hygienic precautions are recommended to avoid any potential public health threats and to safeguard the health of raw milk consumers.
2022-01-01T00:00:00ZPotential use of Chlorella vulgaris KCBAL01 from a freshwater stream receiving treated textile effluent in hexavalent chromium [Cr(VI)] removal in extremely acidic conditionsAththanayake, A. M. K. C. B.Rathnayake, I. V. N.Deeyamullab, M. P.Megharaj, Mallavarapuhttp://repository.kln.ac.lk/handle/123456789/253782022-10-31T07:06:02Z2022-01-01T00:00:00ZPotential use of Chlorella vulgaris KCBAL01 from a freshwater stream receiving treated textile effluent in hexavalent chromium [Cr(VI)] removal in extremely acidic conditions
Aththanayake, A. M. K. C. B.; Rathnayake, I. V. N.; Deeyamullab, M. P.; Megharaj, Mallavarapu
Remediation of hexavalent chromium with conventional chemical and physical methods is a costly
process, while replacing some critical steps in physiochemical remediation with self-sustaining bioremediation
agents are expected to be cost-effective and environmentally friendly implementation.
In this study, a microalga isolated from a freshwater stream receiving treated textile
wastewater was identified up to its molecular level and investigated its ability to tolerate and
remove hexavalent chromium from extremely acidic conditions under different temperatures. The
ability of microalgae to tolerate and remove Cr(VI) was investigated by growing it in BG11 media
with different pH (1, 2, 3 & 7), amended with several concentrations of Cr(VI) and incubated under
different temperatures for 96 hrs. Microalga was identified as Chlorella vulgaris and found that the
isolated strain has a higher hexavalent chromium removal potential in extremely acidic conditions
than in neutral pH conditions at 25 C. In contrast, its Cr(VI) removal potential is significantly influenced
by the pH and temperature of the growth medium. Furthermore, it exhibited a permanent
viability loss at extreme acidic conditions (pH 1 3) and prolonged exposure to the higher chromium
content. The microalga investigated will be a highly useful bioagent in hexavalent chromium
remediation in high acidic conditions.
2022-01-01T00:00:00Z