Janet M. Strong-Gunderson

Insect Cold-hardiness and Ice Nucleating Active Microorganisms Including Their Potential Use for Biological Control

Abstract Since most insects are unable to survive internal ice formation a key factor in their overwintering survival is the regulation of the temperature at which they spontaneously freeze. To enhance their supercooling capacity overwintering insects eliminate endogenous ice nucleators, accumulate low-molecular-weight polyols and sugars, and synthesize hemolymph antifreeze proteins. A number of freeze-tolerant species contain proteins/lipoproteins or insoluble crystals that are ice nucleating active at relatively high subzero temperatures. Only recently have ice nucleating active bacteria and fungi been identified as normal flora in the gut of insects. These microorganisms are the most efficient class of heterogeneous ice nucleators that have been found in insects. Ice nucleating active microorganisms can regulate the supercooling capacity of insects when ingested or applied topically. These unique microorganisms may offer a novel means for the biological control of insect pests during the winter.

Alternative method for rapidly screening microbial isolates for their potential to degrade volatile contaminants.

SummaryA method is described for rapidly screening the metabolic potential of bacteria to oxidize semivolatile and volatile compounds as a sole carbon source. The method is based on automated system that utilizes MicroplatesTM manufactured by Biolog, Inc. (Hayward, CA, USA). This system detects bacterial respiratory activity from the oxidation of a carbon source introduced in volatile form. This is in contrast to the original design, which is based on inoculating a carbon source directly into each well. The 96-well (MT) microtiter plates contain nutrients and a tetrazolium dye. When a bacterial species is capable of oxidizing a volatile carbon substrate, the dye turns purple, and a spectrophotometric plate reader quantifies the response. As a test of this method 150 isolates, including isolates known to degrade some of the test compounds and negative controls were evaluated for their potential to oxidize carbon tetrachloride, toluene, ando-xylene. Thirty-seven isolates (25%) were qualitatively identified as contaminant oxidizers, and thirteen of these (35%) showed significant degradation capabilities for both toluene ando-xylene.

Bioremediation in oil-contaminated sites: bacteria and surfactant accelerated remediation

In Mexico, there are several environmental issues which are being addressed under the current governmental legislation. One important issue is restoring sites belonging to Petroleos Mexicanos (PEMEX). PEMEX is a large government owned oil company that regulates and manages the oil reserves. These sites are primarily contaminated with weathered hydrocarbons which are a consequence of extracting millions of barrels of oil. Within the southern regions of Mexico there are sites which were contaminated by activities and spills that have occurred during the past 30 years. PEMEX has taken the leadership in correcting environmental problems and is very concerned about cleaning up the contaminated sites as quickly as possible. The most significant contaminated sites are located to the north of Veracruz and south of Tabasco. These sites areas are close to refineries or locations of oil exploration. The primary category of contaminants are hydrocarbons, among them asphaltens, aromatic and other contaminants. The concentration of the contaminants varies depending on the location of the sites, but it can reach as high as 500,000 ppm. PEMEX has been searching for appropriate, and cost- effective technologies to clean up these sites. Biologically based remediation activities are of primary interest to PEMEX. However, other treatment technologies such as chemical-physical methods, encapsulation and incineration are also being considered. The present report summarizes preliminary experiments that measured the feasibility of bioremediation for a contaminated site in southern Mexico.