Topic
Bacteria
About: Bacteria is a research topic. Over the lifetime, 23676 publications have been published within this topic receiving 715990 citations. The topic is also known as: eubacteria.
Papers published on a yearly basis
Papers
More filters
TL;DR: This study demonstrates that in some larval species, indigenous gut bacteria contribute to B. thuringiensis susceptibility, and the contribution of enteric bacteria to host mortality suggests that perturbations caused by toxin feeding induce otherwise benign gut bacteria to exert pathogenic effects.
Abstract: Gut microbiota contribute to the health of their hosts, and alterations in the composition of this microbiota can lead to disease. Previously, we demonstrated that indigenous gut bacteria were required for the insecticidal toxin of Bacillus thuringiensis to kill the gypsy moth, Lymantria dispar. B. thuringiensis and its associated insecticidal toxins are commonly used for the control of lepidopteran pests. A variety of factors associated with the insect host, B. thuringiensis strain, and environment affect the wide range of susceptibilities among Lepidoptera, but the interaction of gut bacteria with these factors is not understood. To assess the contribution of gut bacteria to B. thuringiensis susceptibility across a range of Lepidoptera we examined larval mortality of six species in the presence and absence of their indigenous gut bacteria. We then assessed the effect of feeding an enteric bacterium isolated from L. dispar on larval mortality following ingestion of B. thuringiensis toxin. Oral administration of antibiotics reduced larval mortality due to B. thuringiensis in five of six species tested. These included Vanessa cardui (L.), Manduca sexta (L.), Pieris rapae (L.) and Heliothis virescens (F.) treated with a formulation composed of B. thuringiensis cells and toxins (DiPel), and Lymantria dispar (L.) treated with a cell-free formulation of B. thuringiensis toxin (MVPII). Antibiotics eliminated populations of gut bacteria below detectable levels in each of the insects, with the exception of H. virescens, which did not have detectable gut bacteria prior to treatment. Oral administration of the Gram-negative Enterobacter sp. NAB3, an indigenous gut resident of L. dispar, restored larval mortality in all four of the species in which antibiotics both reduced susceptibility to B. thuringiensis and eliminated gut bacteria, but not in H. virescens. In contrast, ingestion of B. thuringiensis toxin (MVPII) following antibiotic treatment significantly increased mortality of Pectinophora gossypiella (Saunders), which was also the only species with detectable gut bacteria that lacked a Gram-negative component. Further, mortality of P. gossypiella larvae reared on diet amended with B. thuringiensis toxin and Enterobacter sp. NAB3 was generally faster than with B. thuringiensis toxin alone. This study demonstrates that in some larval species, indigenous gut bacteria contribute to B. thuringiensis susceptibility. Moreover, the contribution of enteric bacteria to host mortality suggests that perturbations caused by toxin feeding induce otherwise benign gut bacteria to exert pathogenic effects. The interaction between B. thuringiensis and the gut microbiota of Lepidoptera may provide a useful model with which to identify the factors involved in such transitions.
168 citations
TL;DR: It is suggested that the antibacterial ability of intestinal bacteria may protect host fish against pathogenic bacteria, to some extent.
168 citations
TL;DR: Carbon transformation in the microcosms was consistently higher when fungi were present in the inoculum as compared to a diverse community of bacteria acting alone, and antagonistic interaction between fungi and bacteria was most likely explained by competition for C substrate.
Abstract: Fungal–bacterial interaction on decomposing beech leaves was investigated in a microcosm experiment Sterilised 1 yr old leaves were inoculated with microbial populations isolated from beech forest soil: bacteria (inoculum B), fungi and bacteria (inoculum F+B), a cellulolytic Humicola sp (inoculum H) and this fungus together with bacteria (inoculum H+B), respectively The data for mineralization rates and fungal activities, the latter determined by a new enzymatic tool, suggested antagonistic interaction between fungi and bacteria Carbon transformation in the microcosms, estimated as C mineralized plus net dissolved organic carbon (DOC) formation, was consistently higher when fungi were present in the inoculum as compared to a diverse community of bacteria acting alone DOC quality was determined as the ability of the carbon to support denitrification with excess nitrate The DOC quality was dependent on the inoculum type: B and F+B treatments resulted in similar DOC quality, but when the Humicola sp was present (H and H+B treatment) the quality was low Thus, in spite of the higher fungal carbon transformation a fungal-mediated flush of DOC made available to heterotrophic bacteria was not observed Taking all data into account, the antagonistic interaction between fungi and bacteria was most likely explained by competition for C substrate
168 citations
TL;DR: The indirect and direct impacts of lactic acid bacteria in cheese with emphasis on carbohydrate fermentation, changes in oxidation-reduction potential, interactions with non-starter bacteria, autolysis, proteolytic and peptidolytic activities, transport of metabolites and flavor production are described.
Abstract: Chesse flavor is a manifestation of complex interactions of volatile and non-volatile flavor-active compounds plus tactual perception. Numerous agents, including lactic acid bacteria, procece the flavou sensations. The effect of lactic acid bacteria is more dominant in cheese varieties with limited growth of secondary flora. This review describes the indirect and direct impacts of lactic acid bacteria in cheese with emphasis on carbohydrate fermentation, changes in oxidation-reduction potential, interactions with non-starter bacteria, autolysis, proteolytic and peptidolytic activities, transport of metabolites and flavor production.
168 citations
TL;DR: Although not fungicidal, extracts from the herb showed significant growth inhibition against all the fungi tested, and the homogenized water extract was particularly inhibitory to the growth of the fungi.
Abstract: Acetone, methanol and water extracts obtained from the shoots of Arctotis arctotoides through shaking and homogenization, were investigated for their antimicrobial activities. Growth inhibition using agar dilution assays was determined against ten selected bacterial and six fungal species. Although not fungicidal, extracts from the herb showed significant growth inhibition against all the fungi tested. The homogenized water extract was particularly inhibitory to the growth of the fungi with inhibitory activity ranging from 50.7 to 95.2% on Aspergillus tamari and Penicillum digitatum, respectively. Acetone and methanol extracts were very active against the Gram positive bacteria. The Gram negative bacteria were, however, more resistant to the extracts than the Gram positive ones. None of the extracts inhibited Klebsiella pneumoniae and Pseudomonous aeruginosa, both Gram negative bacteria.
168 citations