Browsing by Subject "bacteria"

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  • Munsch-Alatossava, Patricia; Käkelä, Reijo; Ibarra, Dominique; Youbi-Idrissi, Mohammed; Alatossava, Tapani (2018)
    Cold storage aims to preserve the quality and safety of raw milk from farms to dairies; unfortunately, low temperatures also promote the growth of psychrotrophic bacteria, some of which produce heat-stable enzymes that cause spoilage of milk or dairy products. Previously, N-2 gas flushing of raw milk has demonstrated significant potential as a method to hinder bacterial growth at both laboratory and pilot plant scales. Using a mass spectrometry-based lipidomics approach, we examined the impact of cold storage [at 6 degrees C for up to 7 days, the control condition (C)], on the relative amounts of major phospholipids (phosphatidylethanolamine/PE, phosphatidylcholine/PC, phosphatidylserine/PS, phosphatidylinositol/PI, and sphingomyelin/SM) in three bovine raw milk samples, and compared it to the condition that received additional N-2 gas flushing (N). As expected, bacterial growth was hindered by the N-2-based treatment (over 4 log-units lower at day 7) compared to the non-treated control condition. At the end of the cold storage period, the control condition (C7) revealed higher hydrolysis of PC, SM, PE, and PS (the major species reached 27.2, 26.7, 34.6, and 9.9 mu M, respectively), compared to the N-2-flushed samples (N7) (the major species reached 55.6, 35.9, 54.0, and 18.8 mu M, respectively). C7 samples also exhibited a three-fold higher phosphatidic acid (PA) content (6.8 mu M) and a five-fold higher content (17.3 mu M) of lysophospholipids (LPE, LPC, LPS, and LPI) whereas both lysophospholipids and PA remained at their initial levels for 7 days in N7 samples. Taking into consideration the significant phospholipid losses in the controls, the lipid profiling results together with the microbiological data suggest a major role of phospholipase (PLase) C (PLC) in phospholipolysis during cold storage. However, the experimental data also indicate that bacterial sphingomyelinase C, together with PLases PLD and PLA contributed to the degradation of phospholipids present in raw milk as well, and potential contributions from PLB activity cannot be excluded. Altogether, this lipidomics study highlights the beneficial effects of N-2 flushing treatment on the quality and safety of raw milk through its ability to effectively hinder phospholipolysis during cold storage.
  • Munsch-Alatossava, Patricia; Alatossava, Tapani (2020)
    Worldwide, the dairy sector remains of vital importance for food production despite severe environmental constraints. The production and handling conditions of milk, a rich medium, promote inevitably the entrance of microbial contaminants, with notable impact on the quality and safety of raw milk and dairy products. Moreover, the persistence of high concentrations of microorganisms (especially bacteria and bacterial spores) in biofilms (BFs) present on dairy equipment or environments constitutes an additional major source of milk contamination from pre- to post-processing stages: in dairies, BFs represent a major concern regarding the risks of disease outbreaks and are often associated with significant economic losses. One consumption trend toward "raw or low-processed foods" combined with current trends in food production systems, which tend to have more automation and longer processing runs with simultaneously more stringent microbiological requirements, necessitate the implementation of new and obligatory sustainable strategies to respond to new challenges regarding food safety. Here, in light of studies, performed mainly with raw milk, that considered dominant "planktonic" conditions, we reexamine the changes triggered by cold storage alone or combined with nitrogen gas (N-2) flushing on bacterial populations and discuss how the observed benefits of the treatment could also contribute to limiting BF formation in dairies.
  • Brek-Laitinen, Grazyna; López Bellido, Jessica; Ojala, Anne (2012)
    The clearwater boreal Lake Vesijärvi experiences annual periods of hypolimnetic hypoxia with unknown consequences for the microbial food web. We quantified the abundance of heterotrophic bacteria, autotrophic picoplankton (APP), nanoflagellates (NF) and ciliates in Lake Vesijärvi throughout the water column and vegetation season and determined how these varied with changes in environmental conditions, including dissolved oxygen concentrations. The abundance and diversity of ciliates increased significantly throughout the water column with the development of thermal stratification and the onset of hypoxia leading to distinct ciliate communities in the oxic epilimnion and hypoxic hypolimnion. Bacterivorous taxa dominated in the hypoxic zone, while in the epilimnion, bacterivorous, algivorous and predatory taxa feeding on other protozoa were present. Seasonal changes in oxygen and temperature explained nearly 80% of variance in ciliate community composition. Changes in total ciliate numbers correlated with seasonal dynamics of bacteria, but not with the dynamics of NF. In the epilimnion, NF were abundant in early spring and their numbers were positively correlated to numbers of prostomatids and haptorids, but not to APP or bacteria. In the hypolimnion, a significant correlation was found between NF and bacteria, but not NF and ciliates. Significant positive correlations between ciliates and bacteria suggest that concentrations of food resources are important in determining the abundance of ciliates in the plankton. Moreover, we recorded close coupling between seasonal dynamics of bacteria and productivity of phytoplankton, including APP.
  • Schalin, Ilmari (Suomen metsätieteellinen seura, 1964)
  • Ruuskanen, Arttu (Helsingin yliopisto, 2018)
    Tutkimuksen tarkoitus: HUS-sairaanhoitopiirin alueella hoidetaan vuosittain satoja suun alueen hammasperäisiä märkäpaiseita. Paiseiden ensisijainen hoito on hammaslääketieteellinen infektiofokukseen kohdistuva hoito, mutta sen tukena käytetään usein mikrobilääkkeitä. Mikrobilääke aloitetaan hammaslääketieteellisen hoidon yhteydessä empiirisesti, koska paisemärästä otettu viljelyvastaus valmistuu vasta myöhemmin. Siksi on tärkeää, että käytettävissä on tietoa suun paiseiden mikrobiologiasta ja mikrobien alueellisesta herkkyystilanteesta. HUS-alueella paiseiden bakteeriviljelytutkimukset tehdään HUSLAB:ssa. Tämän tutkimuksen tarkoituksena oli selvittää neljän vuoden ajalta hammasperäisissä paiseissa todetut bakteerilöydökset sekä löydösten mikrobilääkeherkkyys. Tutkimuksessa saatua tietoa voidaan käyttää empiirisen lääkehoidon valinnan tukena suun alueen paiseissa. Materiaalit ja menetelmät: Tutkimusaineistona oli HUSLAB:ssa vuosina 2012-2015 aikana tutkitut suun märkäpaiseiden bakteeriviljelytulokset. Viljelylöydöksistä tutkittiin saadut mikrobilöydökset ja löydösten mikrobilääkeherkkyydet. Näytteitä oli yhteensä n=1239. Tulokset: Yleisin löydös oli anaerobi gram-negatiivinen sauvasekafloora (739 näytettä). Tämän jälkeen yleisimmät löydökset olivat alfahemolyyttisiin streptokokkeihin kuuluvat Streptococcus anginosus- ryhmän streptokokit (267 näytettä) ja muut Viridans-ryhmän streptokokit (233 näytettä) sekä anaerobeihin gram-positiivisiin kokkeihin kuuluva Parvimonas micra-ryhmä (261 näytettää). Myös Candida albicans oli varsin yleinen löydös (189 näytettä). Tutkimuksessa havaittiin, että anaerobi gram-negatiivinen sauvasekafloora oli merkittävässä osassa löydöksiä resistentti usein empiirisessä hoidossa käytettävälle penisilliinille, mutta herkkä metronidatsolille. Sen sijaan Viridans-ryhmän streptokokeista valtaosa oli penisilliinille herkkiä. Sen sijaan Viridans-ryhmän streptokokkien herkkyys klindamysiinille on HUS-sairaanhoitopiirin alueella jonkin verran heikentynyt. Johtopäätökset: Suun alueen paiseissa on tyypillisesti sekä aerobeja että anaerobeja bakteereja sisältävää sekaflooraa, jonka löydökset tutkituin osin ovat pääsääntöisesti herkkiä penisilliinin ja metronidatsolin yhdistelmälle. Vain harvoin näytteissä todetaan esim. Staphylococcus aureusta, johon kyseinen lääkeyhdistelmä ei tehoa. Tutkimuksen tulokset tukevat toukokuussa 2017 julkaistun päivitetyn Hammasperäiset äkilliset infektiot ja mikrobilääkkeet Käypä hoito -suosituksen suosittelemia ensisijaisia mikrobilääkkeitä akuuttien suun alueen märkäpaiseiden hoidossa.
  • Lindstrom, Stafva; Timonen, Sari; Sundstrom, Liselotte (2021)
    In a subarctic climate, the seasonal shifts in temperature, precipitation, and plant cover drive the temporal changes in the microbial communities in the topsoil, forcing soil microbes to adapt or decline. Many organisms, such as mound-building ants, survive the cold winter owing to the favorable microclimate in their nest mounds. We have previously shown that the microbial communities in the nest of the ant Formica exsecta are significantly different from those in the surrounding bulk soil. In the current study, we identified taxa, which were consistently present in the nests over a study period of three years. Some taxa were also significantly enriched in the nest samples compared with spatially corresponding reference soils. We show that the bacterial communities in ant nests are temporally stable across years, whereas the fungal communities show greater variation. It seems that the activities of the ants contribute to unique biochemical processes in the secluded nest environment, and create opportunities for symbiotic interactions between the ants and the microbes. Over time, the microbial communities may come to diverge, due to drift and selection, especially given the long lifespan (up to 30 years) of the ant colonies.