  We are studying star formation effects on the properties of the ISM in low
metallicity environments using mid-infrared (MIR) and far-infrared (FIR)
observations of starbursting dwarf galaxies taken with the Infrared Space
Observatory (ISO) and the Kuiper Airborne Observatory (KAO). Effects of the
hard pervasive radiation field on the gas and dust, due to the dust-poor
environments are apparent in both the dust and gas components. From a 158
micron [CII] survey we find enhanced I[CII]/FIR ratios in dwarf galaxies and
I[CII]/I(CO) ratios up to 10 times higher than those for normal metallicity
starburst galaxies. We consider MIR observations in understanding the star
formation properties of dwarf galaxies and constraints on the stellar SED.
Notably, the strong MIR [NeIII]/[NeII] ratios reveal the presence of current
massive stellar populations < 5 My old in NGC1569, NGC1140 and IIZw40. The MIR
unidentified infrared bands (UIBs) are weak, if present at all, as a general
characteristic in low metallicity environments, revealing the destruction of
the smallest carbon particles (e.g. PAHs) over large spatial scales. This is
confirmed with our dust modeling: mass fractions of PAHs are almost negligible
compared to the larger silicate grains emitting in the FIR as well as the small
carbon grains emitting in the MIR, which appear to be the source of the
photoelectric gas heating in these galaxies, in view of the [CII] cooling.
