Browsing by Subject "biocontrol"

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  • Ahlberg, Sara; Randolph, Delia; Okoth, Sheila; Lindahl, Johanna (2019)
    Aflatoxins continue to be a food safety problem globally, especially in developing regions. A significant amount of effort and resources have been invested in an attempt to control aflatoxins. However, these efforts have not substantially decreased the prevalence nor the dietary exposure to aflatoxins in developing countries. One approach to aflatoxin control is the use of binding agents in foods, and lactic acid bacteria (LAB) have been studied extensively for this purpose. However, when assessing the results comprehensively and reviewing the practicality and ethics of use, risks are evident, and concerns arise. In conclusion, our review suggests that there are too many issues with using LAB for aflatoxin binding for it to be safely promoted. Arguably, using binders in human food might even worsen food safety in the longer term.
  • Xu, Ping (Helsingin yliopisto, 2019)
    Heterobasidion is a conifer pathogen that causes tremendous economic loss across the northern hemisphere. It is a root rot pathogen and Heterobasidion infected wood can no longer be used as timber. On spruce the decay is usually observed only in the final cutting, on pines it is visible earlier as the tree dies. It is a worldwide pathogen that is quite common in Europe, Asia and north America. Scientists have yet to find an effective way to treat this disease. The use of viruses against Heterobasidion as a biocontrol method has shown new promise to cure it. In nature, Heterobasidion partitivirus stays inside their host fungus and often shows no symptoms. It was believed before that each type of partitivirus has its own host Heterobasidion species and does not transfer to other Heterobasidion species. However, previous studies have shown that partitivirus is able to transfer to new Heterobasidion host in laboratory and in field, and surprisingly can cause growth rate decrease in its new host. Researchers have previously studied the effects of many partitivirus species on Heterobasidion, but they have focused on analyzing the effects caused by only one virus strain at a time. This thesis focuses on studying the transmission of multiple partitiviruses to a new Heterobasidion host, and on understanding how mixed partitivirus infections affect the growth rate of their new host. To study the transmission of many viruses, two different fungus species both hosting five different partitiviruses were selected as donor fungus strains, and ten different virus-free Heterobasidion fungus strains were selected as recipient fungus strains. Then growth rate experiment was conducted to figure out whether and how multiple viruses infection affect the growth rate of Heterobasidion. The results of this thesis show: 1) It is possible for multiple partitiviruses to transfer to new Heterobasidion hosts. Among 40 transmission experiments, in 13 experiments the recipients were successfully infected by two or more partitiviruses and in 9 experiments the recipients were successfully infected by three or more partitiviruses. 2) Partitiviruses transmission from H. parviporum to H. annosum is considerably less effective than from H. parviporum to H. parviporum. This enlightens us that partitiviruses are easier to be transmitted within species border than across species border. 3) Growth rate experiments showed that multiple virus infection has diverse effects on the growth rate of Heterobasidion hosts. It can be debilitating or beneficial, or sometimes there is no significant change. The growth rate experiments also showed that infection by multiple viruses does not mean more debilitating effects on the growth rate. In conclusion, it is possible to infect Heterobasidion isolates with multiple partitiviruses to generate new virus-host combinations to be tested as putative biocontrol strains. However, more experiments need to be done regarding more virus compositions and more recipients. In the future, it will be interesting to compare the influence of single virus and multiple virus infections.
  • Kauppinen, Ari; Siponen, Sallamaari; Pitkänen, Tarja; Holmfeldt, Karin; Pursiainen, Anna; Torvinen, Eila; Miettinen, Ilkka T. (2021)
    Bacteriophage control of harmful or pathogenic bacteria has aroused growing interest, largely due to the rise of antibiotic resistance. The objective of this study was to test phages as potential agents for the biocontrol of an opportunistic pathogen Pseudomonas aeruginosa in water. Two P. aeruginosa bacteriophages (vB_PaeM_V523 and vB_PaeM_V524) were isolated from wastewater and characterized physically and functionally. Genomic and morphological characterization showed that both were myoviruses within the Pbunavirus genus. Both had a similar latent period (50-55 min) and burst size (124-134 PFU/infected cell), whereas there was variation in the host range. In addition to these environmental phages, a commercial Pseudomonas phage, JG003 (DSM 19870), was also used in the biocontrol experiments. The biocontrol potential of the three phages in water was tested separately and together as a cocktail against two P. aeruginosa strains; PAO1 and the environmental strain 17V1507. With PAO1, all phages initially reduced the numbers of the bacterial host, with phage V523 being the most efficient (>2.4 log(10) reduction). For the environmental P. aeruginosa strain (17V1507), only the phage JG003 caused a reduction (1.2 log(10)) compared to the control. The cocktail of three phages showed a slightly higher decrease in the level of the hosts compared to the use of individual phages. Although no synergistic effect was observed in the host reduction with the use of the phage cocktail, the cocktail-treated hosts did not appear to acquire resistance as rapidly as hosts treated with a single phage. The results of this study provide a significant step in the development of bacteriophage preparations for the control of pathogens and harmful microbes in water environments.
  • Leon-Velarde, Carlos G.; Jun, Jin Woo; Skurnik, Mikael (2019)
    One of the human- and animal-pathogenic species in genus Yersinia is Yersinia enterocolitica, a food-borne zoonotic pathogen that causes enteric infections, mesenteric lymphadenitis, and sometimes sequelae such as reactive arthritis and erythema nodosum. Y. enterocolitica is able to proliferate at 4 degrees C, making it dangerous if contaminated food products are stored under refrigeration. The most common source of Y. enterocolitica is raw pork meat. Microbiological detection of the bacteria from food products is hampered by its slow growth rate as other bacteria overgrow it. Bacteriophages can be exploited in several ways to increase food safety with regards to contamination by Y. enterocolitica. For example, Yersinia phages could be useful in keeping the contamination of food products under control, or, alternatively, the specificity of the phages could be exploited in developing rapid and sensitive diagnostic tools for the identification of the bacteria in food products. In this review, we will discuss the present state of the research on these topics.