The ability of marine bacteria to adhere to detrital particulate organic matter and rapidly switch on metabolic genes in an effort to reproduce is an important response for bacterial survival in the pelagic marine environment. The goal of this investigation was to evaluate the relationship between chitinolytic gene expression and extracellular chitinase activity in individual cells of the marine bacterium Pseudoalteromonas sp. strain S91 attached to solid chitin. A green fluorescent protein reporter gene under the control of the chiA promoter was used to evaluate chiA gene expression, and a precipitating enzyme-linked fluorescent probe, ELF-97-N-acetyl-␤-D-glucosaminide, was used to evaluate extracellular chitinase activity among cells in the bacterial population. Evaluation of chiA expression and ELF-97 crystal location at the single-cell level revealed two physiologically distinct subpopulations of S91 on the chitin surface: one that was chitinase active and remained associated with the surface and another that was non-chitinase active and released daughter cells into the bulk aqueous phase. It is hypothesized that the surface-associated, non-chitinase-active population is utilizing chitin degradation products that were released by the adjacent chitinase-active population for cell replication and dissemination into the bulk aqueous phase.

Growth of the chitin-degrading marine bacterium S91 on solid surfaces under oligotrophic conditions was accompanied by the displacement of a large fraction of the surface-derived bacterial production into the flowing bulk aqueous phase, irrespective of the value of the surface as a nutrient source. Over a 200-h period of surface colonization, 97 and 75% of the bacterial biomass generated on biodegradable chitin and a nonnutritional silicon surface, respectively, detached to become part of the free-living population in the bulk aqueous phase. Specific surface-associated growth rates that included the cells that subsequently detached from the substrata varied depending on the nutritional value of the substratum and during the period of surface colonization. Specific growth rates of 3.79 and 2.83 day ؊1 were obtained when cells first began to proliferate on a pure chitin film and a silicon surface, respectively. Later, when cell densities on the surface and detached cells as CFU in the bulk aqueous phase achieved a quasi-steady state, specific growth rates decreased to 1.08 and 0.79 day ؊1 on the chitin and silicon surfaces, respectively. Virtually all of the cells that detached from either the chitin or the silicon surfaces and the majority of cells associated with the chitin surface over the 200-h period of surface colonization displayed no detectable expression of the chitin-degrading genes chiA and chiB. Cells displaying high levels of chiA-chiB expression were detected only on the chitin surface and then only clustered in discrete areas of the surface. Surface-associated, differential gene expression and displacement of bacterial production from surfaces represent adaptations at the population level that promote efficient utilization of limited resources and dispersal of progeny to maximize access to new sources of energy and maintenance of the population.In the marine environment, hydrolysis of particulate organic matter (POM) to low-molecular-weight dissolved organic matter (DOM) is mediated primarily by ectohydrolytic enzymes produced by particle-associated bacteria (25). While some of the DOM derived from POM hydrolysis is respired as CO 2 , a portion is used for new bacterial production (BP) (53). It has also been hypothesized that a significant portion of the DOM derived from enzymatic attack of POM by POM-associated bacteria supports maintenance and reproduction of free-living bacteria in the pelagic marine environment (3, 9). In fact, POM-associated bacteria are thought to provide more DOM for production of the free-living bacterial populations than for production of POM-associated populations (4, 20, 45, 51). However, detachment of POM-derived cells could lead to overestimation of dissolved organic carbon-derived, free-living BP. Jacobsen and Azam (23) reported that bacteria associated with copepod fecal pellets were displaced into the surrounding water during fecal pellet degradation. While these researchers recognized the potential importance of detachment as a process that contributes to free-livin...

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Head capsule width was used to determine the instar specific phenology of the leafroller Pandemis pyrusana Kearfott and the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), attacking apple in Washington state during 2001-2003. In total, 7012 P. pyrusana and 6122 obliquebanded leafroller larvae were measured from apple orchards from mid-March to mid-September. Degree-day accumulations from each site were paired with the head capsule data to determine the periods during which different instars were present in the field. The implications of this work for pest management and biological control of leafrollers is discussed.

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The fungal pathogen, Entomophaga maimaiga causes epizootics in population s of the important North American forest defoliator gypsy moth (Lymantria dispar). Increasing use of this fungus for biologica l control is dependent on our ability to produce and manipulate the long-lived overwintering resting spores (azygospores). E. maimaiga resting spores undergo obligate dormancy before germination so we investigated conditions required for survival during dormancy as well as the dynamics of subsequent germination. After formation in the Weld during summer, resting spores were stored under various moisture levels, temperatures, and with and without soil in the laboratory and Weld. The following spring, for samples maintained in the Weld, germination was greatest among resting spores stored in plastic bags containing either moistened paper towels or sterile soil. Resting spores did not require light during storage to subsequently germinate. In the laboratory, only resting spores maintained with either sterile or unsterilized soil at 4ë C (but not at 20 or 2 20ë C) germinated the following spring, but at a much lower percentage than most Weld treatments. To further investigat e the eVects of relative humidity (RH) during storage, Weld-collected resting spores were placed at a range of humidities at 4ë C. After 9.5 months, resting spore germination was highest at 58% RH and no resting spores stored at 88 or 100% RH germinated. To evaluate the dynamics of infections initiated by resting spores after storage, gypsy moth larvae were exposed to soil containing resting spores that had been collected in the Weld and stored at 4ë C for varying lengths of time. No diVerences in infection occurred among larvae exposed to fall-collected soil samples stored at 4ë C over the winter, versus soil samples collected from the same location the following spring. Springcollected resting spores stored at 4ë C did not go into secondary dormancy. At the time that cold storage of soil containing resting spores began in spring, infection among exposed larvae was initiated within a few days after bringing the soil to 15ë C. This same pattern was also found for spring-collected resting spore-bearing soil that was assayed after cold storage for 2± 7 months. However, after 31± 32 months in cold storage, infections started 14± 18 days after soil was brought to 15ë C, indicating a delay in resting spore activity after prolonged cold storage.