  Using Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS)
observations of one of the most metal-poor dwarf star-forming galaxies (SFG) in
the local Universe, J2229+2725, we have discovered an extremely strong nebular
CIV 1549, 1551 emission-line doublet, with an equivalent width of 43A, several
times higher than the value observed so far in low-redshift SFGs. Together with
other extreme characteristics obtained from optical spectroscopy (oxygen
abundance 12+log(O/H)=7.085+/-0.031, ratio O32 = I([OIII]5007)/I([OII]3727) ~
53, and equivalent width of the Hbeta emission line EW(Hbeta) = 577A), this
galaxy greatly increases the range of physical properties for dwarf SFGs at low
redshift and is a likely analogue of the high-redshift dwarf SFGs responsible
for the reionization of the Universe. We find the ionizing radiation in
J2229+2725 to be stellar in origin and the high EW(CIV 1549,1551) to be due to
both extreme ionization conditions and a high carbon abundance, with a
corresponding log C/O = -0.38, that is ~ 0.4 dex higher than the average value
for nearby low-metallicity SFGs.
