Mesocosm-scale evaluation of faunal and microbial communities of aerated and unaerated leachfield soil

Do the Invasive Earthworms Amynthas agrestis (Oligochaeta: Megascolecidae) and Lumbricus rubellus (Oligochaeta: Lumbricidae) Stimulate Oxalate-Based Browser Defenses in Jack-in-the-Pulpit (Arisaema triphyllum) by Their Presence or Their Soil Biogeochemical Activity?

The introduction of invasive earthworms initiates physical and chemical alterations in previously earthworm-free forest soils, which triggers an ecological cascade. The most apparent step is the shift in the herbaceous plant community composition. However, some species, such as Arisaema triphyllum (jack-in-the-pulpit), persist where earthworms are present. It has been hypothesized that A. triphyllum produces insoluble oxalate, an herbivory deterrent, in the presence of earthworms. This study aimed to distinguish between the effects of earthworm-induced changes in soils and the physical presence of earthworms on oxalate production. As such, a two-way factorial greenhouse trial was conducted using uninvaded soils to test this hypothesis for two invasive earthworm species (Amynthas agrestis and Lumbricus rubellus). The sequential extraction of oxalates in A. triphyllum corms was performed with absolute ethanol, deionized water, acetic acid and HCl, representing fractions of decreasing solubility. Earthworm presence increased water-soluble (p = 0.002) and total oxalate (p = 0.022) significantly, but only marginally significantly for HCl-soluble oxalate (p = 0.065). The corms of plants grown in soils previously exposed to the two species did not differ in oxalate production when earthworms were not present. However, the data suggest that earthworms affect corm oxalate concentrations and that the sequence of invasion matters for oxalate production by A. triphyllum.

Survival and replication of Mycoplasma species in recycled bedding sand and association with mastitis on dairy farms in Utah

Mycoplasma spp., usually Mycoplasma bovis, are important bovine pathogens that can cause mastitis, metritis, pneumonia, and arthritis. The currently documented routes of transmission of Mycoplasma spp. are through contaminated milking equipment and by direct animal contact. The existence of environmental sources for Mycoplasma spp. and their role in transmission and clinical disease is poorly characterized. Mycoplasma spp. (confirmed as M. bovis in 2 of 4 samples tested using PCR) was found in recycled bedding sand originating from a dairy experiencing an outbreak of clinical mycoplasma mastitis. Mycoplasma spp. were subsequently found in bedding sand from 2 other dairies whose bulk-tank milk was mycoplasma-positive. The association between the occurrence of Mycoplasma spp. in recycled bedding sand and mycoplasma mastitis in cows was further investigated using a pile of recycled sand from dairy 1. Study objectives included the determination of factors associated with the concentration of Mycoplasma spp. in recycled bedding sand and the duration of survival of mycoplasmas in the sand. We also evaluated the efficacy of 2 disinfectants at 2 different concentrations each for the elimination of Mycoplasma spp. from contaminated sand. Mycoplasma spp. survived in the sand pile for 8 mo. The concentration of Mycoplasma spp. within the sand pile was directly related to temperature and precipitation. It was also positively associated with the growth of gram-negative microorganisms, suggesting the possibility of the formation of a biofilm. Ideal temperatures for replication of Mycoplasma spp. occurred between 15 and 20 degrees C. Moisture in the sand and movement of the sand pile also appeared to play a role in replication of mycoplasmas. We found that 0.5% sodium hypochlorite or 2% chlorhexidine were efficacious in eliminating Mycoplasma spp. from contaminated bedding sand. Recycled bedding sand could be an environmental source of Mycoplasma spp., including M. bovis, infections in dairy cows. Future studies should investigate the contribution of this environmental source to the epidemiology of mycoplasma infections in dairy cattle.

Microbial diversity of septic tank effluent and a soil biomat

Microbial diversity of septic tank effluent (STE) and the biomat that is formed as a result of STE infiltration on soil were characterized by 16S rRNA gene sequence analysis. Results indicate that microbial communities are different within control soil, STE, and the biomat and that microbes found in STE are not found in the biomat. The development of a stable soil biomat appears to provide the best on-site water treatment or protection for subsequent groundwater interactions of STE.

Effects of tetracycline on water quality, soil and gases in aerated and unaerated leachfield mesocosms

We examined the effects of tetracycline (TET) addition on the function of mesocosms representing aerated and unaerated septic system leachfields. Replicate mesocosms (n = 3) were filled with soil and either vented to a leachfield (LEACH) or aerated intermittently to maintain an O(2) level of approximately 0.21 mol mol(-1) (AIR). All mesocosms were dosed every 6 h for 10 d with 3 cm of domestic wastewater amended with 5 mg TET L(-1). Water quality parameters, headspace gas composition, and soil properties were measured prior to and during the dosing period, and for 42 days after the last antibiotic dose. No significant effect of TET was observed on the pH, level of dissolved O(2) or dissolved organic carbon (DOC) in drainage water from either treatment. In contrast, levels of Fe(2+) and SO(4) in drainage water from LEACH mesocosms decreased in response to TET dosing, with lower levels persisting until Day 52. Persistent increases were observed in the level of NO(3) in drainage water from AIR lysimeters and in NH(4) in LEACH mesocosms in response to TET additions. Removal of total P and DOC were unaffected by TET dosing in either treatment. Nitrogen removal in AIR mesocosms decreased during the TET dosing period, returning to pre-dosing values by Day 52. In contrast, TN removal in LEACH mesocosms increased during TET dosing, returning to pre-dosing values by Day 52. The composition of headspace gases in AIR mesocosms was not affected by tetracycline dosing. TET dosing resulted in significant increases in soil NH(4) concentration in LEACH mesocosms, whereas significant decreases were apparent in AIR mesocosms. Elevated levels of H(2)S and CH(4) in the headspace of LEACH mesocosms coincided with TET dosing and returned to pre-dosing levels when antibiotic dosing ceased. The effects of tetracycline on leachfield mesocosms differed as a function of aeration. Although most effects were transient, with values returning to pre-dosing levels after a 6-week recovery period in both treatments, persistent effects were observed in LEACH mesocosms.